US6898114B2 - Memory device capable of stable data writing - Google Patents

Memory device capable of stable data writing Download PDF

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US6898114B2
US6898114B2 US10/440,157 US44015703A US6898114B2 US 6898114 B2 US6898114 B2 US 6898114B2 US 44015703 A US44015703 A US 44015703A US 6898114 B2 US6898114 B2 US 6898114B2
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current
write
current source
memory device
memory array
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US20040100819A1 (en
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Hideto Hidaka
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Renesas Electronics Corp
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Renesas Technology Corp
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    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11C—STATIC STORES
    • G11C11/00—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor
    • G11C11/02—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements
    • G11C11/14—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements using thin-film elements
    • G11C11/15—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements using thin-film elements using multiple magnetic layers

Definitions

  • the present invention relates to a memory device, and more particularly to a nonvolatile memory device including a memory cell having a characteristic in that a pass current at the time of data reading is changed in response to a level of binary storage data.
  • An MRAM device is a non-volatile memory device in which non-volatile data storage is performed using a plurality of thin film magnetic elements formed in a semiconductor integrated circuit and a random access is enabled to each of the thin film magnetic elements.
  • a thin film magnetic elements including a magnetic tunnel junction (MTJ) has been used as a memory cell in recent years and thereby a drastic progress in performance of an MRAM device has been achieved, which is disclosed in the following literature.
  • a memory cell having a magnetic tunnel junction therein (hereinafter, also referred to as an “MTJ memory cell”) can be constructed of one MTJ element and one access element (e.g., a transistor), the memory cell is also advantageous in high integration.
  • An MTJ element has a magnetic layer capable of being magnetized along a direction corresponding to an applied magnetic field, and an MTJ memory cell performs data storage using a characteristic in that an electric resistance (a junction resistance) in the MTJ element alters depending on a magnetic direction of the magnetic layer. Whether or not a magnetic direction of the magnetic layer alters is determined by a strength of the synthetic magnetic field of two magnetic fields generated by data write currents flowing in a write digit line and a bit line, respectively.
  • a write digit line and a bit line are also collectively referred to as a write current line, and data write currents are also simply referred to as a write current.
  • data reading is performed based on a pass current through an MTJ memory cell altering depending on an electric resistance (i.e., storage data).
  • a path length of wiring to a MTJ memory cell from a current source supplying a current for writing data to the selected MTJ memory cell is different according to a location of the MTJ memory cell (hereinafter, also referred to as a selected memory cell). Therefore, wiring resistance from the current source to the selected memory cell is different according to the location of the selected memory cell. Therefore, a write current fluctuates in value, which leads to a loss of a margin of data writing, thereby resulting in a possibility to produce a phenomenon to disable data to be normally written to the selected memory cell.
  • a current wire connected to a plurality of write current lines provided correspondingly to each of the predetermined units of a plurality of MTJ memory cells is generally longer than a write current line. Therefore, a large parasitic capacitance is generated on the current wire.
  • An object of the present invention is to provide a memory device capable of supplying a stable current to a memory cell at the time of data writing, and reducing a probability of erroneous writing.
  • a memory device includes a memory cell array in which a plurality of memory cells are arranged through each of which a pass current when data is read flows at a value different according to a level of data written according to an applied data write current.
  • the memory cell array is divided into a plurality of regions each selectable independently of the others as an object for data writing, and the memory device further includes a plurality of current supply sections provided correspondingly to the plurality of regions, respectively.
  • Each of the plurality of current supply sections when a corresponding region of the plurality of regions is selected as the object for data writing, is activated to supply the data write current to the corresponding region, each of the plurality of regions includes a plurality of write select lines provided correspondingly to each of predetermined units of the plurality of memory cells, and the plurality of write select lines are selectively supplied with the data write current from a corresponding one of the plurality of current supply sections.
  • a memory device can reduce a wiring length from a current supply section to a region including a memory cell selected as an object for data writing. As a result, since wiring resistance from the current supply section to the selected memory cell is reduced, fluctuations in writing currents can be decreased, thereby enabling reduction in probability of erroneous writing to a memory cell.
  • a memory device includes: a plurality of memory cells through each of which a pass current when data is read flows at a value different according to a level of data written according to an applied data write current; a plurality of write select lines provided correspondingly to predetermined units of the plurality of memory cells; a current supply line connected electrically to the plurality of write select lines; a plurality of current supply circuits, when data is written, supplying the data write current to the current supply line; and a ground wire for, when data is written, guiding the data write current supplied to the current supply line to at least one of the plurality of ground nodes through at least one of the plurality of write select lines.
  • the plurality of current supply circuits and the plurality of ground nodes are arranged so that a path length of the data write current along the current supply line, a write select line corresponding to a selected memory cell of the plurality of memory cells corresponding to an input address and the ground wire is almost constant regardless of a location of the selected memory cell.
  • a main advantage of the present invention lies in that since a path length of a data write current can be held to be almost constant regardless of a location of a selected memory cell, a stabilization of a write current can be achieved, thereby realization of a memory device capable of reducing a probability of erroneous writing to a memory cell.
  • a memory device includes: a plurality of memory cells through each of which a pass current when data is read flows at a value different according to a level of data written according to an applied data write current; a plurality of write select lines provided correspondingly to predetermined units of the plurality of memory cells; a current supply line connected electrically to the plurality of write select lines; a current supply circuit, when data is written, activated to connect the current supply line electrically to a first power supply voltage and to thereby supply the data write current to the current supply line; an address decode circuit, receiving supply of a second power supply voltage to operate and to decode an input address, and for, when data is written, selecting a write select line to receive supply of the data write current from the plurality of write select lines; and a voltage detecting circuit, connected electrically to the second power supply voltage, and for detecting whether or not the address decode circuit has been activated.
  • the current supply circuit includes a switch for disconnecting the current supply line electrically from the first power supply voltage according to a result of the detection of the voltage detecting circuit when the address decode circuit is in an inactive state, and a voltage level supplied by the first power supply voltage is higher than that supplied by the second power supply voltage.
  • still another advantage of the present invention lies in that the current supply circuit is activated according to an active state of the address decode circuit, thereby enabling realization of a memory device capable of preventing erroneous writing of data when power supply is turned on.
  • FIG. 1 is a schematic diagram showing a configuration of a non-volatile memory device according to a first embodiment
  • FIG. 2 is a circuit diagram showing a configuration of a memory array in a memory array block
  • FIG. 3 is a conceptual diagram describing a structure of an MTJ memory cell and a principle of data storage therein;
  • FIG. 4 is a conceptual diagram showing a relationship between a data write current in an MTJ memory cell and a magnetic direction of a tunneling magneto-resistance element
  • FIGS. 5 and 6 are schematic diagrams showing configurations of non-volatile memory devices of first and second modifications of the first embodiment, respectively;
  • FIGS. 7 and 8 are circuit diagrams showing configurations of memory arrays in memory array blocks according to the first embodiment
  • FIGS. 9 to 11 are schematic diagrams showing configurations of memory arrays according to second to fourth modifications of a second embodiment, respectively;
  • FIG. 12 is a schematic diagram showing a configuration of a non-volatile memory device according to a third embodiment
  • FIG. 13 is a circuit diagram showing a configuration of a memory array in a memory array block according to the third embodiment
  • FIGS. 14 and 15 are schematic diagrams showing configurations of non-volatile memory devices according to the first and second modifications of the third embodiment, respectively;
  • FIGS. 16 and 17 are circuit diagrams showing configurations of memory arrays in memory array blocks according to the third embodiment.
  • FIGS. 18 to 20 are schematic diagrams showing configurations of memory arrays according to second to fourth modifications of a fourth embodiment, respectively;
  • FIG. 21 is a diagram showing details of one of memory blocks in a memory array mat of a non-volatile memory device according to the first embodiment
  • FIG. 22 is a schematic diagram showing a configuration of a non-volatile memory device according to a fifth embodiment
  • FIG. 23 is an operating waveform diagram describing operations in generation of a write current in a non-volatile memory device according to the fifth embodiment
  • FIG. 24 is an operating waveform diagram describing operations when power is turned on of a non-volatile memory device according to the fifth embodiment
  • FIG. 25 is a schematic diagram showing a configuration of a non-volatile memory device according to a first modification of the fifth embodiment
  • FIG. 26 is an operating waveform diagram describing operations in generation of a write current of a non-volatile memory device according to the first modification of the fifth embodiment
  • FIG. 27 is a schematic diagram showing a configuration of a non-volatile memory device according to a second modification of the fifth embodiment
  • FIG. 28 is circuit diagram showing a configuration of the interior of an address decode control circuit
  • FIG. 29 is an operating waveform diagram showing operations in generation of a write current in a non-volatile memory device according to the second modification of the fifth embodiment
  • FIG. 30 is a diagram showing details of one of memory array blocks in a memory array mat of a non-volatile memory device according to the third embodiment
  • FIGS. 31 to 33 are schematic diagrams showing configurations of non-volatile memory devices according to third to fifth modifications of the fifth embodiment, respectively;
  • FIG. 34 is a schematic diagram showing a configuration of a non-volatile memory device to which decoupling capacitance is connected according to a sixth embodiment
  • FIGS. 35 to 37 are schematic diagrams showing configurations of non-volatile memory devices to each of which decoupling capacitance is connected according to first to third modifications of the sixth embodiment, respectively;
  • FIG. 38 is a schematic diagram showing a configuration of a non-volatile memory device according to a fourth modification of the sixth embodiment.
  • FIG. 39 is a circuit diagram showing an address decode circuit provided in the interior of a row decoder
  • FIG. 40 is an operating waveform diagram describing operations in a case where a non-volatile memory device according to the fifth embodiment enters a write state in error when power is turned on;
  • FIG. 41 is an operating waveform diagram describing operations when power is turned on in a non-volatile memory device according to the fourth modification of the sixth embodiment
  • FIG. 42 is a schematic diagram showing a configuration of a non-volatile memory device according to a fifth modification of the six embodiment.
  • FIG. 43 is a circuit diagram showing an address decode circuit provided in the interior of a row decoder
  • FIG. 44 is an operating waveform diagram describing operations in a case where a non-volatile memory device according to the third modification of the fifth embodiment enters a write state in error when power is turned on;
  • FIG. 45 is an operating waveform diagram describing operations when power is turned on in a non-volatile memory device according to the fifth modification of the sixth embodiment.
  • FIG. 46 is a schematic diagram showing a configuration of a non-volatile memory device according to a sixth modification of the sixth embodiment
  • FIG. 47 is a circuit diagram showing a configuration of a one-shot pulse generation control circuit
  • FIG. 48 is an operating waveform diagram describing operations in a case where a non-volatile memory device according to the sixth modification of the sixth embodiment enters a write state in error when power is turned on;
  • FIG. 49 is a schematic diagram showing a configuration of a non-volatile memory device according to a seventh modification of the sixth embodiment.
  • FIG. 50 is a schematic diagram showing a configuration of a non-volatile memory device according to a seventh embodiment
  • FIG. 51 is a circuit diagram showing a configuration of a memory array in a memory array block according to the seventh embodiment.
  • FIGS. 52 and 53 are schematic diagrams showing configurations of non-volatile memory devices according to first and second modifications of the seventh embodiment, respectively;
  • FIG. 54 is a conceptual diagram showing a configuration of a memory array in a memory array block according to an eighth embodiment
  • FIG. 55 is a conceptual diagram showing a configuration of a memory array in a memory array block according to a first modification of the eighth embodiment.
  • FIGS. 56 to 58 are schematic diagrams showing configurations of memory arrays according to second to fourth modifications of the eighth embodiment, respectively.
  • a non-volatile memory device 1000 includes memory array mats 100 and 200 , power supply terminals 10 and 20 , and current sources I 1 and I 2 .
  • Memory array mats 100 and 200 are divided into a plurality of memory array blocks MAB, respectively.
  • memory array mats 100 and 200 are divided into four memory blocks MAB, respectively.
  • each of memory array blocks MAB includes, as an example, a plurality of memory cells arranged in rows and columns, an address decoder, bit lines, write digit lines and read word lines.
  • a memory array mat may be configured so that one address decoder selects a bit line, a write digit line and a read word line included in a plurality of memory array blocks.
  • a power supply voltage Vcc is supplied to power supply terminals 10 and 20 from outside.
  • Power supply terminals 10 and 20 supply power supply voltage Vcc to current sources I 1 and I 2 , respectively.
  • Current source I 1 supplies a current to each of memory array blocks MAB in memory array mat 100 through a current source wire LEI.
  • Current source I 2 supplies a current to each of memory array blocks MAB in memory array mat 200 through a current source wire LE 2 .
  • Current sources I 1 and I 2 supply currents to each of memory array blocks MAB in memory array mats 100 and 200 through current source wires LE 1 and LE 2 , respectively. Note that in the following description, a signal having a main symbol attached with an additional symbol “/” before itself is an inverted signal of an signal having only the main symbol not attached with the symbol “/”.
  • FIG. 2 is a circuit diagram showing a configuration of a memory array 500 in memory array block MAB. Note that in FIG. 2 , there is also shown current source I 1 not included in memory array 500 for convenience in description.
  • memory array 500 includes a memory cell array 55 and a row decoder 50 .
  • Memory cell array 55 has a plurality of MTJ memory cells.
  • the MTJ memory cells are classified into normal memory cells (hereinafter, also simply referred to as a “memory cell MC”) and dummy memory cells DMC arranged in a row direction.
  • a row on which dummy memory cells DMC are arranged is hereinafter also referred to as a “dummy cell row.”
  • Dummy memory cells DMC have the same characteristics (a shape and structure) as memory cell MC and arranged so as to share a memory cell row with memory cells MC.
  • a tunneling magneto-resistance element TMR has a ferromagnetic layer having a fixed magnetic direction (hereinafter, also simply referred to as a “fixed magnetic layer) FL, and a ferromagnetic layer capable of being magnetized in a direction corresponding to an externally applied magnetic field hereinafter, also simply referred to as a “free magnetic layer”) VL.
  • a tunneling barrier (tunneling film) TB made of an insulating film is provided between fixed magnetic layer FL and free magnetic layer VL. Free magnetic layer VL is magnetized in a direction in parallel or anti-parallel to a magnetic direction of fixed magnetic layer FL depending on a level of storage data to be written.
  • a magnetic tunnel junction is formed of fixed magnetic layer FL, tunneling barrier TB and free magnetic layer VL.
  • An electric resistance of tunneling magneto-resistance element TMR alters depending on a relative relationship in magnetic direction between fixed magnetic layer FL and free magnetic layer VL.
  • an electric resistance of tunneling magneto-resistance element TMR takes the minimum value Rmin in a case where magnetic directions of free magnetic layer VL and fixed magnetic layer FL are the same as (in parallel to) each other, while taking the maximum value Rmax in a case where magnetic directions of both layers are opposite to each other (in anti-parallel).
  • read word line RWL When data is written, read word line RWL is deactivated to turn off access transistor ATR. In this state, data write currents for magnetizing free magnetic layer VL flow in directions depending on a level of write data in bit line BL and write digit line WDL.
  • the abscissa H (EA) is used for plotting a magnetic field applied in a magnetic easy axis (EA) direction in free magnetic layer VL in tunneling magneto-resistance element TMR.
  • the ordinate H (HA) is assigned to a magnetic field acting in a magnetic hard axis (HA) direction in free magnetic layer VL therein.
  • Magnetic fields H (EA) and H (HA) correspond to magnetic fields generated by respective currents flowing in bit line BL and write digit line WDL.
  • a fixed magnetic direction of fixed magnetic layer FL is present along a magnetic easy axis of free magnetic layer VL and free magnetic layer VL is magnetized in parallel to (the same as) or anti-parallel to (opposite to) the magnetic direction of fixed magnetic layer FL along the magnetic easy axis depending on a level of storage data in an MTJ memory cell.
  • An MTJ memory cell can store 1 bit data corresponding to one of two magnetic directions of free magnetic layer VL.
  • a magnetic direction of free magnetic layer VL can be rewritten only when the sum of applied magnetic fields H (EA) and H (HA) amounts to a point in a region outside an Astroid characteristic curve shown in FIG. 4 . That is, if an applied data write magnetic field is of a strength in a region inside the Astroid characteristic curve, no change in magnetic direction occurs in free magnetic layer VL.
  • An operating point when data is written is designed to be located so that when predetermined currents are caused to flow in write digit line WDL and bit line BL, storage data in an MTJ memory cell, that is, a magnetic direction of tunneling magneto-resistance element TMR can be rewritten.
  • a data write magnetic field in a magnetic easy axis in an MTJ memory cell which is an object for data writing, is designed so that a strength of the magnetic field takes H WR at an operating point shown in FIG. 4 as an example. That is, a value of a data write current flowing bit line BL or write digit line WDL is designed so that the data write magnetic field H WR is obtained.
  • a magnetic direction once written to tunneling magneto-resistance element TMR that is, storage data of an MTJ memory cell is held in a non-volatile manner till new data writing is performed.
  • read word lines RWL 1 to RWLn and write digit lines WDL 1 to WDLn are provided correspondingly to memory cell rows shared between memory cells MC and dummy memory cells DMC, respectively.
  • a bit line pair BLP are provided correspondingly to memory cell columns constituted of memory cells MC, respectively, and a dummy digit line DDL is provided correspondingly to a dummy cell row.
  • Bit line pair BLP is constituted of two bit lines /BL and BL complementary to each other. While no dummy digit line DDL is used in data writing, it is used when current source wires are precharged, which will be described later.
  • Memory cells MC in an odd-numbered row are connected to one bit line BL, while memory cells MC in an even-numbered row are connected to the other bit line /BL.
  • Each memory cell MC has tunneling magneto-resistance element TMR acting as a magnetic storage section electric resistance of which alters depending on a level of storage data, and an access transistor ATR acting as an access gate, both being connected in series with each other.
  • a MOS transistor is used as access transistor ATR, which is a field effect transistor formed on a semiconductor substrate.
  • Tunneling magneto-resistance element TMR is magnetized in one of two directions to set an electric resistance value thereof to one of Rmin and Rmax.
  • Memory array 500 further includes row decode transistors RD 1 to RDn, dummy row decode transistor RDd, and current source wire L 1 and L 1 #.
  • read word lines RWL 1 to RWLn write digit lines WDL 1 to WDLn and row decode transistors RD 1 to RDn are also collectively referred to as read word line RWL, write digit line WDL and row decode transistor RD, respectively.
  • a current source wire connecting a current source outside a memory array mat electrically to the one memory array block is connected electrically to a current source wire to which a current source in the memory array is connected electrically when the current source is connected electrically to the current source wire in the memory array.
  • current source wire LE 1 connecting current source I 1 electrically to each memory array block MAB is connected electrically to current source line L 1 in FIG. 2 to which current source I 1 is connected electrically.
  • a current source wire corresponding to current source wire L 1 for supplying a write current to desired write digit line WDL is also present in other memory array blocks.
  • each of the current source lines in the other memory array blocks in memory array mat 100 is connected electrically to current source wire LE 1 outside memory array mat 100 . Therefore, in the following description, for example, in a case where a voltage state on and a current amount flowing in current source wire L 1 are shown in an operating waveform diagram, a similar operating waveform diagram is also shown with respect to a current source wire in each of the other memory array blocks.
  • Each row decode transistors RD is provided between write digit line WDL and current source line L 1 #.
  • N-channel MOS transistors are used as each of row decode transistors RD in a configuration in which a current is supplied to a memory array from a current source
  • P-channel MOS transistors are used as each of row decode transistors RD in a configuration in which a current is supplied to a current source from a memory array.
  • Each of the gates of row decode transistors RD are connected to row decoder 50 .
  • Dummy row decode transistor RDd is provided between dummy digit line DDL and current source L 1 #.
  • An N-channel MOS transistor is used as dummy row decode transistor RDd in a configuration in which a current is supplied to a memory array from a current source, while a P-channel MOS transistor is used as dummy row decode transistor RDd in a configuration in which a current is supplied to a current source from a memory array.
  • the gate of dummy row decode transistor RDd is connected to a row decoder 50 .
  • Row decoder 50 sends a signal at H level to the gate of desired row decode transistor RD or dummy row decode transistor RDd according to a row address signal to connect desired write digit line WDL electrically to current source wire L 1 # or connect dummy digit line DDL electrically to current source wire L 1 #.
  • Row decoder 50 is activated when a supplied voltage is raised to a value equal to or more than a predetermined level.
  • Current source wire L 1 is connected electrically to current source I 1 through a current source wire LE 1 (not shown). A predetermined current is supplied to current source wire L 1 from current source I 1 . An end of current source wire L 1 # is connected to ground voltage GND and the other end thereof is set to be in a floating state.
  • Memory array 500 further includes a column select gate CGS, a precharge-equalize circuit P/E and data lines DB and /DB, all being provided to each bit line pair BLP.
  • N-channel MOS transistors 44 and 45 are provided between bit line /BL and data line /DB and between bit line BL and data line DB, respectively. If a column select signal CSLj is inputted to the gates of N-channel MOS transistors 44 and 45 when data is read from memory cell MC, N-channel MOS transistors 44 and 45 connect bit lines /BL and BL electrically to data lines /DB and DB, respectively.
  • bit lines /BL and BL are inputted to a sense amplifier (not shown) through data lines /DB and DB to be amplified there.
  • Precharge-equalize circuit P/E has N-channel MOS transistors 41 , 42 and 43 .
  • N-channel MOS transistors 41 and 43 are provided between bit lines /BL and BL and ground voltage GND, respectively.
  • N-channel MOS transistor 42 is provided between bit lines /BL and BL.
  • memory array 500 further includes bit line drivers 30 a and 30 and a data write circuit 40 , which are provided correspondingly to each memory cell column.
  • Bit line driver 30 a has driver transistors 33 and 34 connected between one end side of a corresponding bit line BL and power supply voltage Vcc and between the one end side of a corresponding bit line BL and ground voltage GND, respectively.
  • bit line driver 30 has driver transistors 31 and 32 connected between the other end side of the corresponding bit line BL and power supply voltage Vcc and between the other end side of the corresponding bit line BL and ground voltage GND, respectively.
  • Driver transistors 33 and 31 are P-channel MOS transistors and driver transistors 34 and 32 are N-channel MOS transistors.
  • Write control signals /WTa 0 and WTa 1 are inputted to the gates of respective driver transistors 33 and 34 , respectively, and write control signals /WTb 0 and WTb 1 are inputted to the gates of respective driver transistors 31 and 32 , respectively.
  • bit line driver 30 a drives the one end side of a corresponding bit line BL with power supply voltage Vcc or ground voltage GND in response to write control signals /WTa 0 and WTa 1 or alternatively, causes the one end side of the corresponding bit line BL to be in a floating state without connecting any of the voltages.
  • bit line driver 30 drives the other end side of the corresponding bit line BL with power supply voltage Vcc or ground voltage GND in response to write control signals /WTb 0 and WTb 1 or alternatively, causes the other end side of the corresponding bit line BL to be in a floating state.
  • Data write circuit 40 controls write control signals /WTa 0 , WTa 1 , /WTb 0 and WTb 1 on each memory cell column according to write data DIN and a result of column selection.
  • Write control signals /WTa 0 , WTa 1 , /WTb 0 and WTb 1 are set so that a data write current +Iw or ⁇ Iw in a direction corresponding to write data DIN flows into bit line BL of a selected column.
  • data write currents +Iw and ⁇ Iw in opposed directions in bit line BL are also collectively referred to as data write current ⁇ Iw.
  • Data write circuit 40 sets write control signals /WTa 0 and /WTb 0 at H level and write control signals WTa 1 and WTb 1 at L level on each memory cell column during a time other than when data is written. Thereby, each bit line BL is set to be in a floating state during a time other than when data is written.
  • data write circuit 40 when data is written, sets each of write control signals /WTa 0 , WTa 1 , /WTb 0 and WTb 1 for a non-selected memory cell column to H level.
  • both ends of bit line BL of a non-selected column when data is written are connected to ground voltage GND so as not to cause a current to flow therein unintentionally.
  • data write circuit 40 when data is written, sets write control signals /WTa 0 , WTa 1 , /WTb 0 and WTb 1 for a selected memory cell column according to write data DIN.
  • write control signals /WTa 0 and WTa 1 are set to L level while write control signals /WTb 0 and WTb 1 are set to H level.
  • data write current +Iw flows in bit line BL of a selected column in a direction from bit line driver 30 a to bit line driver 30 .
  • write control signals /WTa 0 and WTa 1 are set to H level while write control signals /WTb 0 and WTb 1 are set to L level.
  • data write current ⁇ Iw flows in bit line BL of a selected column in a direction from bit line driver 30 to bit line driver 30 a .
  • drive voltages of bit line drivers 30 a and 30 can also be set to independent voltages different from ground voltage GND or power supply voltage Vcc.
  • a data write magnetic field along a magnetic easy axis (EA) is applied to MTJ memory cell MC by data write current ⁇ Iw.
  • EA magnetic easy axis
  • non-volatile memory device 1000 further includes a control circuit 800 .
  • Control circuit 800 outputs a current control signal ICNT 1 or ICNT 2 according to a control signal CT generated in an internal circuit (not shown) according to an address signal.
  • Current sources I 1 and I 2 are activated by current control signals ICNT 1 and ICNT 2 , respectively.
  • Control signal CT is set so that control circuit 800 transmits current control signal ICNT 1 to current source I 1 when a write operation is performed on a memory cell in a memory array block MAB of memory array mat 100 , that is, when memory array mat 100 is selected as an object for data writing.
  • control signal CT is set so that control circuit 800 transmits current control signal ICNT 2 to current source I 2 when a write operation is performed on a memory cell in a memory array block MAB of memory array mat 200 . Note that no specific limitation is imposed on one memory array block, which becomes an object for writing, but a plurality of memory array blocks may simultaneously be objects for writing.
  • one memory array mat is divided into two parts and current sources are provided correspondingly to each of the parts of the memory array mat and the current sources are selectively activated, thereby enabling a wiring length from a current source to a selected memory cell to be halved. Therefore, since wiring resistance from a current source to a selected memory cell is also halved, fluctuations in write currents can be reduced.
  • non-volatile memory device 1000 as described above, a stable current, when data is written, can be supplied to a memory cell to reduce a probability for erroneous writing.
  • a non-volatile memory device 1100 is different from non-volatile memory device 1000 according to the first embodiment shown in FIG. 1 by comparison in an aspect that wiring lengths of current source wire LE 1 from current source I 1 to memory array blocks MAB of memory array mat 100 are equal to each other and wiring lengths current source wire LE 2 from current source I 2 to memory array blocks MAB of memory array mat 200 are equal to each other. Since the other constituents in the configuration and operations therein are the same as in non-volatile memory device 1000 , none of detailed descriptions thereof will be repeated.
  • non-volatile memory device 1100 can reduce fluctuations in wiring lengths from a current source to memory array blocks MAB to a lower value than non-volatile memory device 1000 .
  • non-volatile memory device 1100 can further reduce fluctuations in write currents to a lower value than non-volatile memory device 1000 in addition to the effect exerted by non-volatile memory device 1000 .
  • a non-volatile memory device 1200 is different from non-volatile memory device 1000 according to the first embodiment shown in FIG. 1 by comparison in an aspect that provided are power supply terminals 10 # 1 , 10 # 2 , 20 # 1 and 20 # 2 and current sources I 1 # 1 , I 1 # 2 , I 2 # 1 and I 2 # 2 instead of power supply terminals 10 and 20 and current sources I 1 and I 2 .
  • Power supply voltage Vcc is supplied to power supply terminals 10 # 1 , 10 # 2 , 20 # 1 and 20 # 2 from outside.
  • Power supply terminals 10 # 1 , 10 # 2 , 20 # 1 and 20 # 2 supply power supply voltage Vcc to current sources I 1 # 1 , I 1 # 2 , I 2 # 1 and I 2 # 2 .
  • Current sources I 1 # 1 and I 1 # 2 supply currents to memory array blocks MAB of memory array mat 100 through current source wire LE 1 .
  • Current sources I 2 # 1 and I 2 # 2 supply currents to memory array blocks MAB of memory array mat 200 through current source wire LE 2 . Since the other constituents in the configuration are the same as in non-volatile memory device 1000 , none of detailed descriptions thereof will be repeated.
  • Control circuit 800 transmits current control signal ICNT 1 to current sources I 1 # 1 and I 1 # 2 according to control signal CT. Control circuit 800 further transmits current control signal ICNT 2 to current sources I 2 # 1 and I 2 # 2 according to control signal CT.
  • control signal CT is set so that control circuit 800 transmits current control signal ICNT 1 to current sources I 1 # 1 and I 1 # 2 .
  • control signal CT is set so that control circuit 800 transmits current control signal ICNT 2 to current sources I 2 # 1 and I 2 # 2 .
  • non-volatile memory device 1200 has an advantage that reduction occurs in wiring lengths to each of memory blocks MAB of memory array mats 100 and 200 from the current sources by connecting two current sources to each of current source wires LE 1 and LE 2 to smaller values than non-volatile memory device 1000 in addition the effect exerted by non-volatile memory device 1000 .
  • non-volatile memory device 1200 can further reduce fluctuations in write currents to a lower value than non-volatile memory device 1000 in addition to the effect exerted by non-volatile memory device 1000 .
  • FIG. 7 is a circuit diagram showing a configuration of a memory array 505 in memory array block MAB according to the first embodiment. Note that since an operation in data write circuit 40 has been described in the first embodiment, no data write circuit 40 is shown in the figure.
  • memory array 505 is different from memory array 500 according to the first embodiment by comparison in an aspect that current source I 1 is connected to one end of current source wire L 1 instead of a point in the vicinity of a center between locations thereon to which write digit lines WDL 1 and WDLn are connected. Since the other constituents in the configuration are the same as in memory array 500 shown in the first embodiment, none of detailed descriptions thereof will be repeated.
  • Current source I 1 connected to current source wire L 1 is located at a position thereon diagonal with respect to ground voltage GND connected to current source wire L 1 #. Therefore, for example, a wiring length from current source I 1 to ground voltage GND connected to current source wire L 1 # when row decode transistor RD 1 is turned on is equal to a wiring length from current source I 1 to ground voltage GND connected to current source wire L 1 # when row decode transistor RD 2 is turned on. That is, even if any memory cell is selected when data is written, a wiring length from current source I 1 to ground voltage GND connected to current source wire L 1 # is constant. Therefore, wiring resistance between current source I 1 and current source wire L 1 # is constant. Accordingly, almost no fluctuation occurs in write currents when data is written.
  • write currents can be stabilized.
  • a memory array 510 is different from memory array 500 according to the first embodiment by comparison in an aspect that ground voltage GND is connected to both ends of current source wire L 1 # instead of one end of current source wire L 1 #.
  • ground voltage GND is connected to both ends of current source wire L 1 # instead of one end of current source wire L 1 #.
  • current source wires L 1 and L 1 # since the configuration is the same as memory array 500 except for current source I 1 , current source wires L 1 and L 1 #, write digit line WDL, dummy digit line DDL, row decode transistor RD, dummy row decode transistor RDd and row decoder 50 , only part necessary for description thereof is shown in the figure.
  • ground voltage GND is connected to both ends of current source wire L 1 #, a stronger force is exerted that fixes current source wire L 1 # to ground voltage GND than in the case of memory array 500 in which ground voltage GND is connected to one end of current source wire L 1 #. Therefore, a current flowing in current source wire L 1 # of memory array 510 is stabilized more than in the configuration of memory array 500 . Furthermore, a wiring length from current source I 1 to ground voltage GND is shorter in memory array 510 than in the configuration of memory array 500 by connecting ground voltage GND to current source wire L 1 # not at only one end but at both ends thereof. Therefore, fluctuations in write currents can be further reduced.
  • write currents can be further stabilized to a higher level than in memory array 500 according to the second embodiment.
  • a memory array 520 is different from memory array 510 according to the first modification of the second embodiment by comparison in an aspect that current sources I 1 # 1 and I 1 # 2 are provided instead of current source I 1 .
  • Memory array 520 is further different from memory array 510 by comparison in an aspect that current sources I 1 # 1 and I 1 # 2 are connected to one end and the other end, respectively, of current source wire L 1 instead of current source I 1 connected to a point in the vicinity of the center between locations on current source wire L 1 to which write digit lines WDL 1 and WDLn are connected.
  • Current sources I 1 # 1 and I 12 supply the same amount of currents as the amount that current source I 1 does. Since the other constituents in the configuration are similar to corresponding constituents in the configuration of memory array 510 , none of detailed descriptions thereof will be repeated. Note that in the following description, current sources I 1 # 1 and I 1 # 2 are also collectively referred to as current source I 1 .
  • a memory array 530 is different from memory array 520 according to the second modification of the second embodiment shown in FIG. 9 by comparison in an aspect that ground voltage GND is connected to a point in the vicinity of the center between locations on current source wire L 1 # to which row decode transistor RD 1 and row decode transistor RDn, respectively, are connected instead of ground voltage GND being connected to both ends of current source wire L 1 #. Since the other constituents in the configuration are the same as in memory array 520 , none of detailed descriptions thereof will be repeated.
  • ground voltage GND in memory array 530 , is connected to one point in the vicinity of the center between locations on current source wire L 1 # to which write digit lines WDL 1 and WDLn, respectively, are connected, a weaker force is exerted that fixes current source wire L 1 # to ground voltage GND than in the case of memory array 520 in which ground voltage GND is connected to both ends of current source wire L 1 #. Therefore, when data is written, a current flowing into write digit line WDL is more destabilized, though to some extent, in memory array 530 than in the configuration of memory array 520 .
  • Fluctuations are reduced in path lengths from current source I 1 to ground voltage GND caused by locations of selected write digit line WDL, when data is written, in memory array 530 to a lower level than in the configuration of memory array 520 .
  • a memory array 540 is different from memory array 530 according to the third modification of the second embodiment shown in FIG. 10 by comparison in aspects that current sources I 1 # 1 and I 1 # 3 are connected to one end and the other end, respectively of current source wire L 1 instead of current sources I 1 # 1 and I 1 # 2 being connected to one end and the other end, respectively, of current source wire L 1 and that current source I 1 # 2 is connected to a point in the vicinity of the center between locations on current source wire L 1 to which respective current sources I 1 # 1 and I 1 # 3 are connected.
  • Memory array 540 is further different from memory array 530 by comparison in an aspect that ground voltage GND is connected to a location on current source wire L 1 # to which row decode transistor RD corresponding to write digit line WDL connected to a point on current source wire L 1 in the vicinity of the center between locations thereon to which current sources I 1 # 1 and I 1 # 2 are connected, instead of ground voltage GND being connected to a point on current source wire L 1 # in the vicinity of the center between locations to which row decode transistor RD 1 and row decode transistor RDn, respectively, are connected.
  • Memory array 540 is further different from memory array 530 by comparison in an aspect that ground voltage GND is connected to a location on current source wire L 1 # to which row decode transistor RD corresponding to write digit line WDL connected to a point on current source line L 1 in the vicinity of the center between locations thereon to which respective current sources I 1 # 2 and I 1 # 3 are connected. Since the other constituents in the configuration are the same as in memory array 530 , none of detailed descriptions thereof will be repeated. Note that in the following description, current sources I 1 # 1 , I 1 # 2 and I 1 # 3 are also collectively referred to as current source I 1 .
  • current source I 1 is connected to three locations on current source wire L 1 and ground voltage GND is connected to two locations on current source wire L 1 #, reduction occurs in fluctuations in path lengths from current source I 1 to ground voltage GND caused by locations of selected digit lines WDL when data is written to a lower level than in the configuration of memory array 530 . Therefore, a current flowing write digit line WDL when data is written is stabilized in memory array 540 to a higher level than in the configuration of memory array 530 .
  • a write current can be further stabilized to a higher level than in memory array 530 according to the third modification of the second embodiment.
  • a non-volatile memory device 1000 a is different from non-volatile memory device 1000 according to the first embodiment by comparison in aspects that memory array mats 100 a and 200 a are provided instead of memory array mats 100 and 200 , that power supply terminals 80 and 90 are provided instead of power supply terminals 10 and 20 , and that current sources I 1 a and I 2 a are provided instead of current sources I 1 and I 2 .
  • Memory array mats 100 a and 200 a are each divided into, as an example, four memory array blocks MAB# in a similar way to the way in memory array mats 100 and 200 . Though details will be described later, each of memory array block MAB# includes, as an example, a plurality of memory cells arranged in rows and columns, an address decoder, bit lines, write digit lines and read word lines. Note that memory array mats 100 a and 200 a may be configured so that a bit line, a write digit line and a read word line included in a plurality of memory array blocks are selected with one address decoder.
  • Non-volatile memory device 1000 a is further different from non-volatile memory device 1000 by comparison in aspects that a current is supplied from each of memory array block MAB# of memory array mat 100 a to current source I 1 a through current source wire LE 1 instead of current source I 1 supplying a current to each memory array block MAB of memory array mat 100 through current source wire LE 1 , and that currents are supplied to current source I 2 a from each memory array block MAB# of memory array mat 200 a through current source wire LE 2 instead of current source I 2 supplying currents to each memory array block MAB of memory array mat 200 through current source wire LE 2 . Since the other constituents in the configuration are similar to corresponding constituents in the configuration of non-volatile memory device 1000 , none of detailed descriptions thereof will be repeated.
  • Current sources I 1 a and I 2 a cause currents to flow to respective power supply terminals 80 and 90 connected to ground voltage GND.
  • Current sources I 1 a and I 2 a are activated according to respective current control signals ICNT 1 and ICNT 2 .
  • FIG. 13 is a circuit diagram showing a configuration of a memory array 500 a in memory array block MAB# according to the third embodiment. Note that in FIG. 13 , there is also shown current source I 1 a not included in memory array 500 a for convenience in description.
  • memory array 500 a is different from memory array 500 according to the first embodiment by comparison in aspects that a row decoder 50 a is included instead of row decoder 50 , that current source I 1 a is connected to current source line L 1 instead of current source I 1 , and that power supply voltage Vcc is connected to one end of current source wire L 1 # instead of ground voltage GND.
  • a P-channel MOS transistor is used as each of row decode transistor RD and a P-channel MOS transistor is used as dummy decode transistor RDd. Since the other constituents in the configuration are similar to corresponding constituents in the configuration of memory array 500 , none of detailed descriptions thereof will be repeated.
  • Row decoder 50 a sends a signal at L level to the gate of desired row decode transistor RD or dummy row decode transistor RDd according to a row address signal to connect desired write digit line WDL electrically to current source wire L 1 # or connect dummy digit line DDL electrically to current source wire L 1 #.
  • control signal CT is set so that control circuit 800 transmits current control signal ICNT 1 to current source I 1 a .
  • control signal CT is set so that control circuit 800 transmits current control signal ICNT 2 to current source I 2 a .
  • non-volatile memory device 1000 a is configured so that currents are supplied to power supply terminals 80 and 90 from memory array blocks MAB# of respective memory array mats 100 a and 200 a
  • one memory array mat is divided into two parts in similar way to the way in non-volatile memory device 1000 to provide current sources correspondingly to respective two memory array mats and to selectively activate one thereof, thereby enabling a wiring length from a current source to a selected memory cell to be halved.
  • wiring resistance from a current source to a selected memory cell is halved, thereby enabling fluctuations in write currents to be reduced.
  • non-volatile memory device 1000 a according to the third embodiment as described above, there can be obtained an effect similar to the effect of non-volatile memory device 1000 according to the first embodiment.
  • a non-volatile memory device 1100 a is different from non-volatile memory device 1000 a according to the third embodiment shown in FIG. 12 by comparison in an aspect that non-volatile memory device 1100 a is configured so that wiring lengths of current source wire LE 1 from memory blocks MAB# of memory array mat 100 a to current source I 1 a are equal to each other and wiring lengths of current source wire LE 2 from memory blocks MAB# of memory array mat 200 a to current source I 2 a are equal to each other. Since the other constituents in the configuration and the operations therein are the same as in the configuration of non-volatile memory device 1000 a , none of detailed descriptions thereof will be repeated.
  • Non-volatile memory device 1100 a therefore, can reduce fluctuations in wiring lengths from selected memory cells in each of memory array blocks MAB of memory array mats 100 a and 200 a to the current source to a lower level than non-volatile memory device 1000 a.
  • non-volatile memory device 1100 a can further reduce fluctuations in write currents to a lower level than non-volatile memory device 1000 a in addition to the effect exerted by non-volatile memory device 1000 a.
  • a non-volatile memory device 1200 a is different from non-volatile memory device 1000 a according to the third embodiment shown in FIG. 12 by comparison in an aspect that power terminals 80 # 1 , 80 # 2 , 90 # 1 and 90 # 2 , and current sources I 1 a # 1 , I 1 a # 2 , I 2 a # 1 and 12 a # 2 are provided instead of power supply terminals 80 and 90 , and current sources I 1 a and I 2 a .
  • Current sources I 1 a # 1 , I 1 a # 2 , I 2 a # 1 and 12 a # 2 are connected to power supply terminals 80 # 1 , 80 # 2 , 90 # 1 and 90 # 2 .
  • Each memory array block MAB# of memory array mat 100 a supplies currents to current sources I 1 a # 1 and I 1 a # 2 through current source wire LE 1 .
  • Each memory array block MAB# of memory array mat 200 a supplies currents to current sources I 2 a # 1 and I 2 a # 2 through current source wire LE 2 .
  • Current sources I 1 a # 1 , I 1 a # 2 , I 2 a # 1 and I 2 a # 2 cause currents to flow into respective power supply terminals 80 # 1 , 80 # 2 , 90 # 1 and 90 # 2 , all connected to ground voltage GND. Since the other constituents in the configuration are similar to corresponding constituents of the configuration of non-volatile memory device 1000 a , none of detailed descriptions thereof will be repeated.
  • Control circuit 800 transmits current control signal ICNT 1 to current sources I 1 a # 1 and I 1 a # 2 according to control signal CT. Control circuit 800 further transmits current control signal ICNT 2 to current sources I 2 a # 1 and I 2 a # 2 according to control signal CT.
  • Current sources I 1 a # 1 and I 1 a # 2 are activated according to current control signal ICNT 1 .
  • Current sources I 2 a # 1 and I 2 a # 2 are activated according to current control signal ICNT 2 .
  • control signal CT is set so that control circuit 800 transmits current control signal ICNT 1 to current sources I 1 a # 1 and I 1 a # 2 .
  • control signal CT is set so that control circuit 800 transmits current control signal ICNT 2 to current sources I 2 a # 1 and I 2 a # 2 .
  • non-volatile memory device 1200 a has an advantage that reduction occurs in wiring lengths to current sources from selected memory cells in memory blocks MAB# of each of memory array mats 100 a and 200 a by connecting the two current sources to each of current source wires LE 1 and LE 2 .
  • non-volatile memory device 1200 a can further reduce fluctuations in write currents to a lower level than non-volatile memory device 1000 a in addition to the effect exerted by non-volatile memory device 1000 a.
  • a memory array 505 a is different from memory array 505 according to the second embodiment shown in FIG. 7 by comparison in aspects that a row decoder 50 a is included instead of row decoder 50 , that current source I 1 a is connected to one end of current source line L 1 instead of current source I 1 , and that power supply voltage Vcc is connected to one end of current source wire L 1 # instead of ground voltage GND.
  • Current source I 1 a is connected to ground voltage GND.
  • a P-channel MOS transistor is used as each of row decode transistors RD and a P-channel MOS transistor is used as dummy row decode transistor RDd. Since the other constituents in the configuration are similar to corresponding constituents in the configuration of memory array 505 , none of detailed descriptions thereof will be repeated.
  • current source I 1 a connected to current source wire L 1 is located at a position thereon diagonal with respect to power supply voltage Vcc connected to current source wire L 1 #.
  • memory array 505 a according to the fourth embodiment there can be obtained an effect similar to the effect of memory array 505 according to the second embodiment.
  • a memory array 510 a is different from memory array 510 according to the first modification of the second embodiment shown in FIG. 8 by comparison in aspects that a row decoder 50 a is included instead of row decoder 50 , that current source I 1 a is connected to current source wire L 1 instead of current source I 1 , and that power supply voltage Vcc is connected to both ends of current source wire L 1 # instead of ground voltage GND.
  • Current source I 1 a is connected to ground voltage GND.
  • a P-channel MOS transistor is used as each of row decode transistors RD and a P-channel MOS transistor is used as dummy row decode transistor RDd. Since the other constituents in the configuration are similar to corresponding constituents in the configuration of memory array 510 , none of detailed descriptions thereof will be repeated.
  • memory array 510 a is configured so that in the configuration of memory array 510 , current sources and ground voltage are reversed in arrangement, an effect similar to the effect of memory array 510 can be obtained.
  • a memory array 520 a is different from memory array 520 according to the second modification of the second embodiment shown in FIG. 9 by comparison in aspects that a row decoder 50 a is included instead of row decoder 50 , that current sources I 1 a # 1 and I 1 a # 2 are connected to one end and the other end, respectively, of current source wire L 1 instead of current sources I 1 # 1 and I 1 # 2 , and that power supply voltage Vcc is connected to both ends of current source wire L 1 # instead of ground voltage GND. Current sources I 1 # 1 and I 1 a # 2 are connected to ground voltage GND.
  • a P-channel MOS transistor is used as each of row decode transistor RD and a P-channel MOS transistor is used as dummy row decode transistor RDd. Since the other constituents in the configuration are similar to corresponding constituents in the configuration of memory array 520 , none of detailed descriptions thereof will be repeated.
  • memory array 520 a is configured so that in the configuration of memory array 520 , current sources and ground voltage are reversed in arrangement, an effect similar to the effect of memory array 520 can be obtained.
  • a memory array 530 a is different from memory array 530 according to the third modification of the second embodiment shown in FIG. 10 by comparison in aspects that a row decoder 50 a is included instead of row decoder 50 , that current sources I 1 a # 1 and I 1 a # 2 are connected to one end and the other end, respectively, of current source wire L 1 instead of current sources I 1 # 1 and I 1 # 2 , and that power supply voltage Vcc is connected to a point on current source wire L 1 # in the vicinity of the center between locations thereon to which row decode transistor RD 1 and row decode transistor RDn are connected instead of ground voltage GND.
  • Current sources I 1 a # 1 and I 1 a # 2 are connected to ground voltage GND.
  • a P-channel MOS transistor is used as each of row decode transistor RD and a P-channel MOS transistor is used as dummy row decode transistor RDd. Since the other constituents in the configuration are similar to corresponding constituents in the configuration of memory array 530 , none of detailed descriptions thereof will be repeated.
  • memory array 530 a is configured so that in the configuration of memory array 530 , current sources and ground voltage are reversed in arrangement, an effect similar to the effect of memory array 530 can be obtained.
  • a memory array 540 a is different from memory array 540 according to the fourth modification of the second embodiment shown in FIG. 11 by comparison in aspects that a row decoder 50 a is included instead of row decoder 50 , that current sources I 1 a # 1 , I 1 a # 2 and I 1 a # 3 are connected to locations on current source wire L 1 to which current sources I 1 # 1 , I 1 # 2 and I 1 # 3 are connected instead of current sources I 1 # 1 , I 1 # 2 and I 1 # 3 , and that power supply voltage Vcc is connected to locations on current source wire L 1 # to which ground voltage GND is connected instead of ground voltage GND.
  • memory array 540 a is configured so that in the configuration of memory array 540 , current sources and ground voltage are reversed in arrangement, an effect similar to the effect of memory array 540 can be obtained.
  • non-volatile memory device 1000 part of non-volatile memory device 1000 described above is shown in detail for comparison with a non-volatile memory device according to this embodiment and description will be given of a problem thereof.
  • FIG. 21 there is shown a configuration of memory array 505 for description in one of memory blocks MAB of non-volatile memory device 1000 .
  • Parasitic capacitances C 1 and C 2 are generated in current source wires LE 1 and L 1 , respectively. Since current source wire L 1 is generally longer than current source wire LE 1 , parasitic capacitance C 2 is larger than parasitic capacitance C 1 .
  • a voltage supplied to a current source for generating a write current is higher than a voltage used in a memory array mat. Therefore, before row decoder 50 is activated when power is turned on, that is, when a possibility exists that write digit line WDL is in a selected state, a current produced from parasitic capacitance C 2 is superimposed on a current from a current source to generate an excessive large current and to thereby, produce a possibility that erroneous data writing is performed on a memory cell arranged in the vicinity of write word line WDL.
  • current source wires LE 1 and L 1 are precharged to ground voltage GND differing from power supply voltage Vcc to thereby prevent generation of an excessive large current.
  • non-volatile memory device 1500 includes a memory array mat 100 , a power supply terminal 10 , a clock terminal 60 , a control terminal 70 , a voltage setting circuit 107 , a control circuit 108 and a current source 110 .
  • Power supply voltage Vcc is supplied to power supply terminal 10 .
  • An external clock Ext.CLK is inputted to clock terminal 60 .
  • An external write signal Ext.WE is inputted to control terminal 70 .
  • Voltage setting circuit 107 includes an N-channel MOS transistor 117 provided between a node NI and ground voltage GND.
  • Control circuit 108 includes inverters 111 , 112 and 118 , and a NOR circuit 113 .
  • Inverter 111 outputs a signal at an inverted level of external clock Ext.CLK inputted from clock terminal 60 .
  • Inverter 112 outputs a signal at an inverted level of external write signal Ext.WE inputted from control terminal 70 .
  • NOR circuit 113 outputs a signal WE obtained by performing a NOR operation on output signals of inverters 111 and 112 . That is, when output signals of inverters 111 and 112 are both at L level, signal WE is set at H level.
  • Inverter 118 inputs a signal at an inverted level of signal WE to the gate of N-channel MOS transistor 117 in voltage setting circuit 107 .
  • Current source 110 includes P-channel MOS transistors 114 and 116 , an N-channel MOS transistor 115 , and a reference voltage generating circuit 119 .
  • P-channel MOS transistor 116 is provided between power supply terminal 10 and node NI.
  • the source and drain of P-channel MOS transistor 114 are connected to power supply voltage Vcc and the gate of P-channel MOS transistor 116 , respectively.
  • the source and drain of N-channel MOS transistor 115 are connected to a connection node between the drain of P-channel MOS transistor 114 and the gate of N-channel MOS transistor 116 , and reference voltage generating circuit 119 , respectively.
  • Signal WE is inputted to the gates of P-channel MOS transistor 114 and N-channel MOS transistor 115 .
  • Node NI is connected to current source wire LE 1 for supplying a current to each memory array block MAB of memory array mat 100 .
  • Reference voltage generating circuit 119 generates a voltage Vref at which a write current flowing in write digit line WDL in memory array mat 100 becomes optimal.
  • Vref is generally set to an intermediate level between power supply voltage Vcc and ground voltage GND.
  • N-channel MOS transistor 117 While N-channel MOS transistor 117 is in the on state during a period in which signal WE is at L level, P-channel MOS transistor 116 is not in the on state. Therefore, during a period in which signal WE is at L level, voltages on current source wires LE 1 and L 1 are precharged to ground voltage GND at all times by an operation of voltage setting circuit 107 .
  • N-channel MOS transistor 117 is turned off while N-channel MOS transistor 115 is turned on. Therefore, since voltage Vref is applied to the gate of P-channel MOS transistor 116 , P-channel MOS transistor 116 is turned on. As a result, voltage levels of current source wires LE 1 and L 1 are set to power supply voltage Vcc.
  • FIG. 23 is an operating waveform diagram describing operations in generation of a write current in a non-volatile memory device 1500 according to the fifth embodiment.
  • LE 1 and L 1 show a change in voltage level of current source wires LE 1 and L 1 .
  • Iw shows a change in write current flowing out from current source 110 .
  • non-volatile memory device 1500 As described above, since current source wires LE 1 and L 1 are normally precharged at ground voltage GND, no charging of parasitic capacitances C 1 and C 2 occurs till generation of a write current. Therefore, an excessively large current is prevented from flowing into write digit line WDL selected by row decoder 50 in memory array mat 100 ; thereby enabling prevention of erroneous data writing when ordinary data writing is performed and when power is turned on as well.
  • Non-volatile memory device 1500 is configured so that current source wires LE 1 and L 1 are normally precharged at ground voltage GND and when data is written, voltage levels of current source wires LE 1 and L 1 are raised to thereby prevent erroneous data writing. In the configuration of non-volatile memory device 1500 , however, if voltage levels of current source wires LE 1 and L 1 are normally precharged at ground voltage GND, a voltage level of current source wire L 1 takes time to be raised to a voltage at which a sufficient write current is supplied, which causes a long time required for data writing to a selected memory cell.
  • a non-volatile memory device 1510 is different from non-volatile memory device 1500 according to the fifth embodiment shown in FIG. 22 by comparison in an aspect that a voltage setting circuit 107 a is provided instead of voltage setting circuit 107 .
  • Voltage setting circuit 107 a supplies intermediate voltage Vpr to the source of N-channel MOS transistor 117 instead of ground voltage GND being connected to the source thereof, compared with the case where voltage setting circuit 107 is used. Since the other constituents in the configuration are similar to corresponding constituents in the configuration of non-volatile memory device 1500 , none of detailed descriptions thereof will be repeated.
  • Intermediate voltage Vpr is set to a voltage equal to or lower than Vw, which is a voltage level at which internal current source wire L 1 causes a sufficient write current to flow into desired write digit line WDL.
  • power supply voltage Vcc is equal to voltage Vw in this embodiment.
  • non-volatile memory device 1510 voltages on current source wires LE 1 and L 1 are always precharged at intermediate voltage Vpr during a period in which signal WE is at L level.
  • signal WE is set to H level
  • voltage levels on current source wires LE 1 and L 1 are set to voltage Vw.
  • FIG. 26 is an operating waveform diagram describing operations in generation of a write current in non-volatile memory device 1510 according to the first modification of the fifth embodiment.
  • LE 1 and L 1 show a change in voltage level of current source wires LE 1 and L 1 .
  • Iw shows a change in write current flowing out from current source 110 .
  • currents generated from parasitic capacitances C 1 and C 2 precharged at intermediate voltage Vpr occur in current source wires LE 1 and L 1 when data is written, an amount of the currents is about a half of the amount when precharging is performed at power supply voltage Vcc, so that an excessively large current can be prevented from flowing into write digit line WDL.
  • current source wire L 1 is precharged at intermediate voltage Vpr and a voltage level of current source wire L 1 can thereby reach a desired voltage faster than when precharging is performed at ground voltage GND, thereby enabling a time required for data writing to a selected memory cell to be shorter.
  • non-volatile memory device 1550 is different from non-volatile memory device 1500 according to the fifth embodiment shown in FIG. 22 by comparison in an aspect that further provided are an address terminal 72 , an internal address generating circuit 150 , a control terminal 260 and a control circuit 300 .
  • Non-volatile memory device 1550 is further different from non-volatile memory device 1500 by comparison in an aspect that a memory array mat 105 is provided instead of memory array mat 100 .
  • Memory array mat 105 is different from memory array mat 100 shown in FIG. 22 by comparison in aspects that a P-channel MOS transistor RDdd is provided between dummy digit line DDL and power supply voltage Vpr supplying intermediate voltage Vpr, that an address decode control circuit 160 is included instead of row decoder 50 , that an inverter 198 is further included and that no dummy row decode transistor RDd is included.
  • Power supply voltage Vpr is set to a voltage equal to or lower than Vw, at which current source wire L 1 can cause a sufficient write current to flow into desired write digit line WDL.
  • Dummy digit line DDL and current source wire L 1 # are electrically disconnected from each other. Since the other constituents in the configuration are similar to corresponding constituents in the configuration of non-volatile memory device 1510 , none of detailed descriptions thereof will be repeated.
  • Inverter 198 inputs a signal at an inverted level of a control signal from address decode control circuit 160 to the gate of P-channel MOS transistor RDdd. That is, P-channel MOS transistor RDdd is turned on by a signal at H level from address decode control circuit 160 . When P-channel MOS transistor RDdd is turned on, current source wire L 1 connected electrically to power supply voltage Vpr is precharged to intermediate voltage Vpr. When a signal at L level is inputted to inverter 198 , P-channel MOS transistor RDdd is turned off.
  • An external address Ext.Add is inputted to address terminal 72 .
  • Internal address generating circuit 150 receives external address signal Ext.Add from address terminal 72 to convert it to an internal row address signal IAdd and to output the latter signal to address decode control circuit 160 .
  • a control signal CNT is inputted to control terminal 260 .
  • Control circuit 300 receives control signal CNT to output a control signal RT to address decode control circuit 160 .
  • address decode circuit 160 includes a row decoder 50 b , a latch circuit 190 , a tri-state buffer 193 , a one-shot pulse generating circuit 170 , a fall detecting circuit 180 , an inverter 194 , and an N-channel MOS transistor 195 .
  • Latch circuit 190 has inverters 191 and 192 therein. Latch circuit 190 holds an inputted signal temporarily to output a signal at an inverted level of the inputted signal.
  • N-channel MOS transistor 195 is provided between node N 1 and ground voltage GND.
  • Control signal RT is inputted to row decoder 50 b and one-shot pulse generating circuit 170 .
  • Internal address signal IAdd is inputted to row decoder 50 b.
  • Row decoder 50 b is activated when control signal RT at H level is inputted thereto. Furthermore, row decoder 50 b , when internal row address signal IAdd is inputted thereto, outputs a signal R for activating desired row decode transistor RDn. Signal R is held temporarily at a data level in latch circuit 190 .
  • One-shot pulse generating circuit 170 includes inverters 171 , 172 and 173 in odd-number (as an example, three inverters) connected in series to each other, and an AND circuit 174 .
  • Control signal RT is inputted to inverter 171 .
  • An output signal of inverter 173 and signal RT are inputted to AND circuit 174 to output a one-shot pulse signal PU obtained by performing an operation of a logical product thereon to inverter 198 and fall detecting circuit 180 .
  • a time during which one-shot pulse signal PU is held at H level which is an output signal, is determined by the number of inverters connected in series with each other and characteristics thereof. That is, with an increased number of inverters, a longer period is obtained during which one-shot pulse signal PU is held at H level.
  • Fall detecting circuit 180 has inverters 181 , 182 , 183 , 184 and 185 in odd-number (as an example, five inverters) connected in series to each other, and NOR circuit 186 therein.
  • One-shot pulse signal PU is inputted to inverter 181 .
  • An output signal of inverter 185 and one-shot pulse signal PU are inputted to NOR circuit 186 to output signal ST obtained by performing an NOR operation thereon.
  • a time in which an output signal thereof is held at H level is determined by the number of inverters connected in series to each other and characteristics thereof. That is, with an increased number of inverters, a longer period is obtained during which output signal ST is held at H level.
  • Tri-state buffer 193 when signal ST at H level is inputted to the control terminal thereof, outputs a signal at an inverted level of data outputted from latch circuit 190 as signal ACT to desired row decode transistor RDn through node N 1 .
  • Inverter 194 outputs a signal at an inverted level of signal ST to the gate of an N-channel MOS transistor 195 .
  • FIG. 29 is an operating waveform diagram showing operations in generation of a write current in non-volatile memory device 1550 according to the second modification of the fifth embodiment.
  • LE 1 and L 1 show a change in voltage level of current source wires LE 1 and L 1 .
  • Iw shows a change in write current flowing out from current source 110 .
  • row decoder 50 b in address decode control circuit 160 .
  • Row decoder 50 b requires a time till it outputs signal R at H level for activating desired row decode transistor RDn. If signal RT takes H level at a time point t 2 in a period till signal R at H level is outputted from row decoder 50 b , one-shot pulse signal PU is outputted from one-shot pulse generating circuit 170 .
  • signal WE takes H level at a time point t 3 when external clock Ext.CLK and external write signal WE both take H level.
  • voltage levels on current source wires LE 1 and L 1 start to rise to power supply voltage Vcc from ground voltage GND. Furthermore, write current Iw flowing out from current source 110 also starts to increase.
  • One-shot pulse signal PU at H level is inputted to inverter 198 and P-channel MOS transistor RDdd is in the on state during a period in which one-shot pulse signal PU is at H level and current source wire L 1 connected electrically to power supply voltage Vpr is precharged to intermediate voltage Vpr. Thereafter, signal R at H level is outputted from row decoder 50 b in address decode control circuit 160 . Signal R at H level is converted to a signal at L level in latch circuit 190 and held temporarily there.
  • Fall detecting circuit 180 when detecting a fall of one-shot pulse signal PU, outputs signal ST at H level.
  • one-shot pulse signal PU takes L level, precharging of current source wire L 1 at intermediate voltage Vpr is canceled.
  • Tri-state buffer 193 when signal ST at H level is inputted to the control terminal thereof, outputs signal R at L level held in latch circuit 190 as signal ACT at H level at time point t 4 to the gate of desired row decode transistor RDn to turn on it. Thereafter, when signal ST takes L level, N-channel MOS transistor 195 is turned on to cause a voltage at node N 1 to be at L level. Simultaneously, signal ST at L level is also inputted to the control terminal of tri-state buffer 193 ; therefore, signal ACT takes L level at a time point t 5 to cause row decode transistor RDn to be turned off.
  • a voltage on current source wire L 1 has reached a voltage capable of causing a sufficient write current to flow into write digit line WDL at a time point t 4 when row decode transistor RDn is turned on, thereby enabling a stable write current to flow into write digit line WDL corresponding to row decode transistor RDn.
  • current source wire L 1 is precharged to an intermediate voltage using dummy digit line DDL in a period during which an address signal is decoded to effectively use the period during which the address signal is decoded, thereby enabling supply of stable write current into desired write digit line WDL.
  • non-volatile memory device 1000 a described above for comparison with a non-volatile memory device according to this embodiment and description will be given of a problem thereof.
  • FIG. 30 for description shown is a configuration of memory array 505 a in one of memory array blocks MAB# of non-volatile memory device 1000 a.
  • Parasitic capacitances C 1 and C 3 are generated on respective current source wires LE 1 and L 1 #. Since current source wire L 1 # is generally longer than current source wire LE 1 , parasitic capacitance C 3 is larger than parasitic capacitance C 1 .
  • non-volatile memory device 1000 a In the configuration of non-volatile memory device 1000 a shown in FIG. 30 , if current source wires LE 1 and L 1 are precharged at ground voltage GND before activation of row decoder 50 a , a current generated from parasitic capacitance C 3 occurring on current source wire L 1 # is superimposed on a write current flowing in selected write word line WDL after activation of row decoder 50 a . Therefore, an excessively large current larger than an ordinary write current is generated in write word line WDL and a possibility arises that erroneous data writing is performed on a non-selected memory cell arranged in the vicinity of selected write word line WDL.
  • current source wires LE 1 and L 1 are precharged at power supply voltage Vcc, differing from the case where current source wires LE 1 and L 1 are precharged at ground voltage GND, thereby preventing generation of an excessively large current.
  • non-volatile memory device 1500 a is different from non-volatile memory device 1500 shown in FIG. 22 by comparison in aspects that a memory array mat 100 a is provided instead of memory array mat 100 and that a power supply terminal 80 is provided instead of power supply terminal 10 .
  • Non-volatile memory device 1500 a is further different from non-volatile memory device 1500 by comparison in an aspect that voltage setting circuit 127 , control circuit 128 and current source 130 are provided instead of voltage setting circuit 107 , control circuit 108 and current source 110 , respectively. Since the other constituents in the configuration are similar to corresponding constituents in the configuration of non-volatile memory device 1500 , none of detailed descriptions thereof will be repeated.
  • Power supply terminal 80 is connected to ground voltage GND. Power supply terminal 80 receives a current from current source 130 .
  • Control circuit 128 includes inverters 131 , 132 and 138 , and a NOR circuit 133 .
  • Inverter 131 outputs a signal at an inverted level of external clock Ext.CLK inputted thereto from clock terminal 60 .
  • Inverter 132 outputs a signal at an inverted level of external write signal Ext.WE inputted thereto from control terminal 70 .
  • NOR circuit 133 outputs signal WE obtained by performing a NOR operation on output signals of inverters 131 and 132 . That is, when output signals of inverters 131 and 132 are both at L level, signal WE is set to H level.
  • Inverter 138 outputs signal /WE at an inverted level of signal WE.
  • Voltage setting circuit 127 includes a P-channel MOS transistor 137 provided between power supply voltage Vcc and node NI. Signal WE is inputted to the gate of P-channel MOS transistor 137 .
  • Current source 130 includes N-channel MOS transistors 134 and 136 , a P-channel MOS transistor 135 , and a reference voltage generating circuit 119 .
  • N-channel MOS transistor 136 is provided between power supply terminal 80 and node NI.
  • the drain and source of N-channel MOS transistor 134 are connected to the gate of N-channel MOS transistor 136 and ground voltage GND, respectively.
  • the drain and source of P-channel MOS transistor 135 are connected to a connection node between the drain of N-channel MOS transistor 134 and the gate of N-channel MOS transistor 136 , and reference voltage generating circuit 119 , respectively.
  • Signal /WE is inputted to the gates of N-channel MOS transistor 134 and P-channel MOS transistor 135 .
  • Reference voltage generating circuit 119 generates voltage Vref so that a write current flowing in write digit line WDL in memory array mat 100 a becomes optimal.
  • Vref is generally set at an intermediate level between power supply voltage Vcc and ground voltage GND.
  • non-volatile memory device 1500 a is configured so that current source wires LE 1 and L 1 are precharged at power supply voltage Vcc before data writing is performed, thereby preventing a data write operation from occurring, a time is required till a voltage level of current source wire L 1 reaches ground voltage GND in the case where current source wires LE 1 and L 1 are precharged at power supply voltage Vcc, which makes a timing of data writing to a selected memory cell delayed. Therefore, description will be given of a configuration for preventing not only generation of an excessively large current in write digit line WDL from occurring, but also making it earlier in timing to perform data writing to the selected memory cell. To be concrete, current source wires LE 1 and L 1 is precharged not to power supply voltage Vcc, but to an intermediate potential.
  • a non-volatile memory device 1510 a is different from non-volatile memory device 1500 a according to the third modification of the fifth embodiment by comparison in an aspect that a voltage setting circuit 127 a is provided instead of voltage setting circuit 127 .
  • intermediate voltage Vpr is connected to the source of P-channel MOS transistor 137 instead of power supply voltage Vcc. Since the other constituents in the configuration are the same in the configuration in non-volatile memory device 1500 , none of detailed descriptions thereof will be repeated.
  • Intermediate voltage Vpr is set to a voltage equal to or less than Vw, which is a voltage level, at which current source wire L 1 # can cause a sufficient write current to flow into desired write digit line WDL.
  • power supply voltage Vcc is equal to voltage Vw.
  • non-volatile memory device 1510 a voltages on current source wires LE 1 and L 1 are in a precharged state at intermediate voltage Vpr during a period in which signal WE is at L level.
  • signal WE is set to H level
  • voltage levels of current source wires LE 1 and L 1 are set to ground Voltage GND.
  • a non-volatile memory device 1550 a is different from non-volatile memory device 1500 a according to the third modification of the fifth embodiment shown in FIG. 31 by comparison in an aspect that further provided are an address terminal 72 , an internal address generating circuit 150 , a control terminal 260 and a control circuit 300 .
  • Non-volatile memory device 1550 a is further different from non-volatile memory device 1500 a by comparison in an aspect that a memory array mat 105 a is provided instead of memory array mat 100 a.
  • Memory array mat 105 a is different from memory array mat 100 a shown in FIG. 31 by comparison in aspects that a P-channel MOS transistor RDdd is provided between dummy digit line DDL and power supply voltage Vpr supplying intermediate voltage Vpr, that an address decode control circuit 160 a is included instead of row decoder 50 a , that an inverter 199 is further provided, and that no dummy row decode transistor RDd is included.
  • a P-channel MOS transistor is used as each of row decode transistor RD.
  • Power supply voltage Vpr is set to a voltage equal to or less than Vw, which is a voltage level, at which current source wire L 1 # can cause a sufficient write current to flow into desired write digit line WDL. Dummy digit line DDL is disconnected electrically from current source wire L 1 #. Since the other constituents in the configuration are similar to corresponding constituents in the configuration of non-volatile memory device 1510 a , none of detailed descriptions thereof will be repeated.
  • Address decode control circuit 160 a is different from address decode control circuit 160 by comparison in an aspect that an output signal of one-shot pulse generating circuit 170 is transmitted to inverter 199 instead of inverter 198 .
  • the other constituents in the configuration and functions of the circuit are similar to corresponding constituents in the configuration and the functions of address decode control circuit 160 .
  • non-volatile memory device 1550 a according to the fifth modification of the fifth embodiment therefore, there can also be obtained an effect similar to the effect of non-volatile memory device 1550 according the second modification of the fifth embodiment.
  • parasitic capacitances C 1 and C 2 occur on current source wires LE 1 and L 1 as described above in the configuration of non-volatile memory device 1000 according to the first embodiment.
  • non-volatile memory device 1000 a voltage supplied to a current source for generating a write current is higher than a voltage used in the interior of a memory array mat. For this reason, if non-volatile memory device 1000 enters a write state by mistake, before row decoder 50 is activated when power is turned on, that is, when a possibility exists that write digit line WDL is in a selected state, a possibility arises that a current generated from parasitic capacitance C 2 is superimposed on a current from a current source to result in an excessively large current and to perform erroneous data writing on a memory cell arranged in the vicinity of write digit line WDL.
  • a configuration can be conceived in which decoupling capacitance for suppressing fluctuations in power supply voltage is provided onto a power supply wire.
  • a high frequency current flowing in a current source wire such as a peak current passes through the decoupling capacitance.
  • a non-volatile memory device 1010 is different from non-volatile memory device 1000 shown in FIG. 21 by comparison in an aspect that decoupling capacitances 600 and 605 are further provided. Since the other constituents in the configuration are similar to corresponding constituents in the configuration of non-volatile memory device 1000 , none of detailed descriptions thereof will be repeated.
  • Decoupling capacitance 600 is connected electrically between a connection node between power supply terminal 10 and current source I 1 , and ground voltage GND.
  • Decoupling capacitance 605 is connected electrically between a connection node between power supply terminal 20 and current source I 2 , and ground voltage GND.
  • non-volatile memory device 1010 can remove peak currents when power is turned on, thereby enabling a stable write current to be supplied.
  • non-volatile memory device 1000 an effect similar to the effect of non-volatile memory device 1010 can also be obtained in non-volatile memory devices 1100 and 1200 by connecting decoupling capacitance electrically between a connection node between a power supply terminal and a current source, and ground voltage GND in a similar way.
  • a non-volatile memory device 1010 a is different from non-volatile memory device 1000 a shown in FIG. 30 by comparison in an aspect that one of memory array blocks MAB# in memory array mat 100 a further includes a decoupling capacitance 610 . Since the other constituents in the configuration are similar to corresponding constituents in the configuration of non-volatile memory device 1000 a , none of detailed descriptions thereof will be repeated.
  • Decoupling capacitance 610 is connected electrically between a connection node between power supply voltage Vcc connected to one end of current source wire L 1 # in memory array block MAB# and dummy row decode transistor RDd, and ground voltage GND. In such a configuration, there can be obtained an effect similar to the effect of non-volatile memory device 1010 according to the sixth embodiment.
  • a memory array 540 b is different from memory array 540 according to the fourth modification of the second embodiment shown in FIG. 11 by comparison in an aspect that decoupling capacitances 620 , 621 and 622 are further provided. Since the other constituents in the configuration are similar to corresponding constituents in the configuration of memory array 540 , none of detailed descriptions thereof will be repeated.
  • Decoupling capacitances 620 , 621 and 622 are connected electrically between each of connection nodes between power supply voltage Vcc and respective current sources I 1 #, I 1 # 2 and I 1 # 3 , and ground voltage GND.
  • memory array 540 b according to the second modification of the sixth embodiment has an advantage that peak currents when power is turned on can be removed; thereby enabling a stable write current to be supplied in addition to the effect exerted by memory array 540 according to the fourth modification of the second embodiment.
  • a memory array 540 c is different from memory array 540 a according to the fourth modification of the fourth embodiment shown in FIG. 20 by comparison in an aspect that decoupling capacitances 630 and 631 are further provided. Since the other constituents in the configuration are similar to corresponding constituents in the configuration of memory array 540 a , none of detailed descriptions thereof will be repeated.
  • Decoupling capacitances 630 and 631 are each connected electrically between a connection node between power supply voltage Vcc and current source wire L 1 #, and ground voltage GND.
  • memory array 540 c according to the third modification of the sixth embodiment has an advantage that peak currents when power is turned on can be removed; thereby enabling a stable write current to be supplied in addition to the effect exerted by memory array 540 a according to the fourth modification of the fourth embodiment.
  • a configuration is only required in which a current source is activated after activation of a row decoder in a non-volatile memory device.
  • a non-volatile memory device 1600 is different from non-volatile memory device 1500 according to the fifth embodiment shown in FIG. 22 by comparison in an aspect that further provided are power supply terminals 73 and 71 , an address terminal 72 and an internal address generating circuit 150 .
  • Non-volatile memory device 1600 is further different from non-volatile memory device 1500 by comparison in aspects that a voltage detecting circuit 159 is further provided, that a control circuit 158 is provided instead of control circuit 108 , that a voltage setting circuit 157 is provided instead of voltage setting circuit 107 , and that a current source 140 is provided instead of current source 110 . Since the other constituents in the configuration are similar to corresponding constituents in the configuration of non-volatile memory device 1500 , none of detailed descriptions thereof will be repeated.
  • External power supply voltage Ext.Vcc 1 is supplied to power supply terminal 73 .
  • External power supply voltage Ext.Vcc 2 is supplied to power supply terminal 71 .
  • power supply voltages Vcc 1 and Vcc 2 are set at 2.5 V and 1.0 V, respectively. Since description has been given of address terminal 72 and internal address generating circuit 150 , neither of detailed descriptions thereof will be repeated.
  • external power supply voltages Ext.Vcc 1 and Ext.Vcc 2 are also referred to as external power supply voltages Vcc 1 and Vcc 2 .
  • Voltage detecting circuit 159 includes a P-channel MOS transistor 149 b and an N-channel MOS transistor 149 c connected in series between power supply voltage Vcc 1 and ground voltage GND. Power supply voltage Vcc 2 is supplied to the gates of P-channel MOS transistor 149 b and N-channel MOS transistor 149 c.
  • Control circuit 158 includes inverters 141 and 142 , a NOR circuit 143 , and an inverter 148 .
  • Inverter 141 is driven by power supply voltage Vcc 1 to output a signal at an inverted level of external clock Ext.CLK inputted from dock terminal 60 .
  • Inverter 142 is driven by power supply voltage Vcc 1 to output a signal at an inverted level of external write signal Ext.WE inputted from control terminal 70 .
  • NOR circuit 143 outputs signal WE obtained by performing a NOR operation on signals outputted from inverters 141 and 142 , and a signal outputted from a connection node N# between P-channel MOS transistor 149 b and N-channel MOS transistor 149 c .
  • Inverter 148 outputs a signal at an inverted level of signal WE. That is, signal WE is set to H level when output signals of inverters 141 and 142 and an output signal of connection node N# are at L levels, respectively.
  • Voltage setting circuit 157 includes an N-channel MOS transistor 147 provided between a node NI 2 and ground voltage GND. A signal at an inverted level of signal WE is inputted to the gate of N-channel MOS transistor 147 .
  • Current source 140 includes P-channel MOS transistors 144 and 146 ; an N-channel MOS transistor 145 , and a reference voltage generating circuit 119 .
  • P-channel MOS transistor 146 is provided between power terminal 73 and node NI 2 .
  • the source and drain of P-channel MOS transistor 144 are connected to power supply voltage Vcc 1 and the gate of P-channel MOS transistor 146 , respectively.
  • the source and drain of N-channel MOS transistor 145 are connected to a connection node between the drain of P-channel MOS transistor 144 and the gate of P-channel MOS transistor 146 , and reference voltage generating circuit 119 , respectively.
  • Signal WE is inputted to the gates of P-channel MOS transistor 144 and N-channel MOS transistor 145 .
  • Node NI 2 is connected to current source wire LE 1 for supplying a current to each of memory array blocks MAB of memory array mat 100 .
  • Reference voltage generating circuit 119 generates voltage Vref at which a write current flowing into write digit line WDL in memory array mat 100 is optimal.
  • Vref is generally set to an intermediate level between power supply voltage Vcc and ground voltage GND.
  • N-channel MOS transistor 147 is turned on, while P-channel MOS transistor 146 is not turned on. Therefore, during a period in which signal WE is at L level, voltages on current source wires LE 1 and L 1 are precharged at ground voltage GND at all times by an action of voltage setting circuit 157 .
  • Voltage Vcc 2 is supplied to row decoder 50 from power supply terminal 71 . Furthermore, an internal row address signal IAdd outputted from internal address generating circuit 150 is inputted to row decoder 50 .
  • FIG. 39 is a circuit diagram showing an address decode circuit 350 provided in the interior of row decoder 50 . Note that for description, write digit line WDLn and row decode transistor RDn are shown in the figure. Address decode circuit 350 is provided correspondingly to each write digit line WDL.
  • Address decode circuit 350 has a NAND circuit 301 and an inverter 302 therein.
  • NAND circuit 301 is driven by power supply voltage Vcc 2 to output a signal /SL at L level when signals X 1 to Xn constituting internal row address signal IAdd for selecting desired write digit line WDLn outputted from internal address generating circuit 150 are all set to H level.
  • Inverter 302 is driven by power supply voltage Vcc 2 to output signal SL, which is an inverted signal of signal /SL. When signal SL is set to H level, row decode transistor RDn is turned on.
  • non-volatile memory device 1600 in order to compare non-volatile memory device 1600 according to this embodiment with non-volatile memory device 1500 according to the fifth embodiment described above, description will be given of a case where non-volatile memory device 1500 enter a write state in error when power is turned on.
  • FIG. 40 is an operating waveform diagram describing operations in a case where non-volatile memory device 1500 according to the fifth embodiment shown in FIG. 22 enters a write state in error when power is turned on.
  • external write signal Ext.WE and external address Ext.Add that selects no write digit line VVDL are simultaneously inputted by mistake to non-volatile memory device 1500 from outside.
  • power supply voltage Vcc 1 is supplied from power supply terminal 10 of non-volatile memory device 1500 and power supply voltage Vcc 2 is supplied to row decoder 50 .
  • external address signal Ext.Add is converted to internal row address signal IAdd in an internal address generating circuit not shown and inputted to row decoder 50 .
  • LE 1 and L 1 show a change in current flowing in current source wires LE 1 and L 1 .
  • WDL shows a change in write current flowing in write digit line WDL.
  • non-volatile memory device 1500 in a case where the memory device entered a write state by mistake when power is turned on.
  • External voltage Ext.Vcc 1 starts to rise at time point t 1 after power is turned on.
  • external address Ext.Add is inputted to an internal address generating circuit and converted to internal row address signal IAdd.
  • external write signal Ext.WE is inputted to inverter 112 . If signal WE takes H level at time point t 3 , voltages on current source wires LE 1 and L 1 starts to rise up to Vcc 1 .
  • NAND circuit 301 driven by power supply voltage Vcc 2 in address decode circuit 350 also starts to become active.
  • internal row address IAdd for not selecting write digit line WDL has been inputted to NAND circuit 301 . That is, when NAND circuit 301 is activated, output signal /SL thereof is set to H level. In a state where no sufficient voltage is supplied to NAND circuit 301 , signal SL outputted from inverter 302 takes H level before /SL takes H level to turn on row decode transistor RDn connected to non-selected write digit line WDL.
  • FIG. 41 is an operating waveform diagram describing operations when power is turned on in a non-volatile memory device 1600 according to the fourth modification of the sixth embodiment. Note that it is considered a case where external write signal Ext.WE and external address Ext.Add that selects no write digit line WDL are simultaneously inputted to non-volatile memory device 1600 from outside.
  • LE 1 and L 1 show a change in current flowing in current source wires LE 1 and L 1 .
  • WDL shows a change in write current flowing in write digit line WDL.
  • non-volatile memory device 1600 when power is turned on using FIGS. 38 , 39 and 4 .
  • external voltage Ext.Vcc 1 starts to rise.
  • external address Ext.Add is inputted to internal address generating circuit 150 and converted to internal row address signal IAdd.
  • external write signal Ext.WE is also inputted to inverter 142 .
  • NAND circuit 301 driven by power supply voltage Vcc 2 in address decode circuit 350 also starts to become active.
  • internal row address signal IAdd not selecting write digit line WDL has been inputted to NAND circuit 301 . That is, output signal /SL of NAND circuit 301 is set to H level when being activated. In a state where no sufficient voltage is supplied to NAND circuit 301 , signal SL outputted from inverter 302 takes H level before /SL takes H level.
  • N-channel MOS transistor 149 c in voltage detecting circuit 159 is turned on to set signal WE to H level.
  • voltages on current source wires LE 1 and L 1 starts to rise up to Vcc 1 .
  • NAND circuit 301 and inverter 302 have been supplied with power supply voltage Vcc 2 ; therefore both normally operate to set signal SL to L level.
  • row decode transistor RDn connected to non-selected write digit line WDL is not turned on. Hence, no current flows in current source wire L 1 and non-selected write digit line WDL, so no erroneous data writing occurs on a memory cell.
  • non-volatile memory device 1600 In non-volatile memory device 1600 according to the fourth modification of the sixth embodiment, as described above, even if the memory device has entered a write state by mistake when power is turned on, erroneous data writing can be prevented since no unnecessary current flows in write digit line WDL.
  • a non-volatile memory device 1600 a is different from non-volatile memory device 1600 according to the fourth modification of the sixth embodiment shown in FIG. 38 by comparison in an aspect that a power supply terminal 80 , a voltage detecting circuit 179 , a control circuit 178 , a voltage setting circuit 177 , a current source 160 and a memory array mat 100 b are provided instead of power supply terminal 73 , voltage detecting circuit 159 , control circuit 158 , voltage setting circuit 157 , current source 140 and memory array mat 100 , respectively. Since the other constituents in the configuration are similar to corresponding constituents in the configuration of non-volatile memory device 1600 , none of detailed descriptions thereof will be repeated.
  • Power supply voltage Vcc 1 is connected to current source wire L 1 # in memory array mat 100 b .
  • Power supply terminal 80 is connected to ground voltage GND to receives a current from current source 160 .
  • Voltage detecting circuit 179 includes a P-channel MOS transistor 169 b and an N-channel MOS transistor 169 c connected in series between power supply voltage Vcc 1 and ground voltage GND. Power supply voltage Vcc 2 is supplied to the gates of P-channel MOS transistor 169 b and N-channel MOS transistor 169 c.
  • Control circuit 178 includes inverters 161 and 162 , a NOR circuit 163 , and an inverter 168 .
  • Inverter 161 is driven by power supply voltage Vcc 1 to output a signal at an inverted level of external clock Ext.CLK inputted from clock terminal 60 .
  • Inverter 162 is driven by power supply voltage Vcc 1 to output a signal at an inverted level of external write signal Ext.WE inputted from control terminal 70 .
  • NOR circuit 163 outputs signal WE obtained by performing a NOR operation on output signals outputted from inverters 161 and 162 , and a connection node N# between P-channel MOS transistor 169 b and N-channel MOS transistor 169 c . That is, signal WE is set to H level when output signals of inverters 161 and 162 , and connection node N# are at L levels, respectively.
  • Inverter 168 outputs signal /WE at an inverted level of signal WE.
  • Voltage setting circuit 177 includes a P-channel MOS transistor 167 provided between power supply voltage Vcc 1 and node NI 2 .
  • Signal WE is inputted to the gate of P-channel MOS transistor 167 .
  • Current source 160 includes N-channel MOS transistors 164 and 166 , a P-channel MOS transistor 165 , and a reference voltage generating circuit 119 .
  • N-channel MOS transistor 166 is provided between power supply terminal 80 and node NI 2 .
  • the source and drain of N-channel MOS transistor 164 are connected to ground voltage GND and the gate of N-channel MOS transistor 166 , respectively.
  • the drain and source of P-channel MOS transistor 165 are connected to a connection node between the drain of N-channel MOS transistor 164 and the gate of N-channel MOS transistor 166 , and reference voltage generating circuit 119 , respectively.
  • Signal /WE is inputted to the gates of N-channel MOS transistor 164 and P-channel MOS transistor 165 .
  • Reference voltage generating circuit 119 generates voltage Vref at which a write current flowing in write digit line WDL in memory array mat 100 b is optimal.
  • Vref is generally set to an intermediate level between power supply voltage Vcc and ground voltage GND.
  • Voltage Vcc 2 is supplied to row decoder 50 a from power supply terminal 71 . Furthermore, internal row address signal IAdd outputted from internal address generating circuit 150 is inputted to row decoder 50 a.
  • FIG. 43 is a circuit diagram showing an address decode circuit 360 provided in the interior of row decoder 50 a . Note that for description, write digit line WDLn and row decode transistor RDn are shown in the figure. Address decode circuit 360 is provided correspondingly to each write digit line WDL.
  • Address decode circuit 360 has a NAND circuit 301 therein.
  • NAND circuit 301 is driven by power supply voltage Vcc 2 to output signal SL at L level when internal row address signals IAdd for selecting desired write digit line WDLn outputted from internal address generating circuit 150 are all set to H level.
  • signal SL is set to L level, row decode transistor RDn is turned on.
  • non-volatile memory device 1600 a In order to compare non-volatile memory device 1600 a according to this embodiment with non-volatile memory device 1500 a according to the third modification of the fifth embodiment described above, description will be given of operations in a case where non-volatile memory device 1500 a enters a write state in error when power is turned on.
  • FIG. 44 is an operating waveform diagram describing operations in a case where non-volatile memory device 1500 a according to the third modification of the fifth embodiment enters a write state in error when power is turned on.
  • external write signal Ext.WE and external address Ext.Add that selects no write digit line WDL are simultaneously inputted by mistake to non-volatile memory device 1500 a from outside.
  • power supply voltage Vcc 1 is supplied to current source wire L 1 # instead of power supply voltage Vcc.
  • power supply voltage Vcc 2 is supplied to row decoder 50 a .
  • external address signal Ext.Add is converted to internal row address signal IAdd in an internal address generating circuit not shown and inputted to row decoder 50 a .
  • L 1 # shows a change in current flowing in current source line L 1 #.
  • WDL shows a change in write current flowing in write digit line WDL.
  • FIG. 45 is an operating waveform diagram describing operations when power is turned on in non-volatile memory device 1600 a according to the fifth modification of the sixth embodiment. Note that in this case, external write signal Ext.WE and external address Ext.Add that selects no write digit line WDL are simultaneously inputted by mistake to non-volatile memory device 1600 a from outside.
  • L 1 # shows a change in current flowing in current source wire L 1 #.
  • WDL shows a change in write current flowing in write digit line WDL.
  • non-volatile memory device 1600 a when power is turned on using FIGS. 42 , 43 and 45 .
  • External voltage Ext.Vcc 1 starts to rise at time point t 1 after power is turned on, Simultaneously, voltages on current source wires LE 1 and L 1 also start to rise.
  • external address Ext.Add is inputted to internal address generating circuit 150 and converted to internal row address signal IAdd.
  • external write signal Ext.WE is inputted to inverter 162 .
  • NAND circuit 301 driven by power supply voltage Vcc 2 in address decode circuit 360 also starts to become active.
  • internal row address signal IAdd not selecting write digit line WDL has been inputted to NAND circuit 301 . That is, when NAND circuit 301 is activated, output signal SL thereof is set to H level. In a state where no sufficient voltage is supplied to NAND circuit 301 , signal SL is at L level.
  • NAND circuit 301 since NAND circuit 301 is supplied with power supply voltage Vcc 2 , the circuit normally operates to set signal SL to H level. Therefore, row decode transistor RDn connected to non-selected write digit line WDL is not turned on. Hence, no current flows in current source wire L 1 # and non-selected digit line WDL, so no chance occurs that erroneous data writing is performed on a memory cell.
  • non-volatile memory device 1600 a in non-volatile memory device 1600 a according to the fifth modification of the sixth embodiment, as described above, the configuration is adopted in which a current flows from a memory array mat to a current source, but there can be obtained an effect similar to the effect of the fourth modification of the sixth embodiment.
  • a non-volatile memory device 1700 is different from non-volatile memory device 1600 according to the fourth modification of the sixth embodiment shown in FIG. 38 by comparison in an aspect that a control circuit 220 is provided instead of control circuit 158 . Since the other constituents in the configuration are similar to corresponding constituents in the configuration of non-volatile memory device 1600 , none of detailed descriptions thereof will be repeated.
  • Control circuit 220 is different from control circuit 158 by comparison in an aspect that a one-shot pulse generation control circuit 310 is included instead of NOR circuit 143 .
  • one-shot pulse generation control circuit 310 has a one-shot pulse generating circuit 320 and a NOR circuit 327 therein.
  • One-shot pulse generating circuit 320 has inverters 321 , 322 , 323 , 324 and 325 in odd-number (as an example, five inverters) connected in series with each other, and a NAND circuit 326 therein.
  • An output signal of inverter 141 is inputted to inverter 321 .
  • An output signal of inverter 325 and an output signal of inverter 141 are inputted to NAND circuit 326 to output a one-shot pulse signal obtained by performing a NAND operation thereon to NOR circuit 327 .
  • a time in which an output signal thereof is held at L level is determined by the number of inverters connected in series with each other and characteristics thereof. That is, with an increased number of inverters, a longer period results, in which the output signal is held at L level.
  • NOR circuit 327 outputs signal WE obtained by performing a NOR operation on an output signal of one-shot pulse generating circuit 320 , an output signal of inverter 142 and an output signal from node N#. That is, NOR circuit 327 sets signal WE to H level by an output signal at L level from inverter 142 , a signal at L level from node N# and an output signal at L level from one-shot pulse generating circuit 320 . A period in which signal WE is held at H level is equal to a period in which an output signal from one-shot pulse generating circuit 320 is held at L level.
  • N-channel MOS transistor 147 is turned on, while P-channel MOS transistor 146 is not turned on. Therefore, during a period in which signal WE is at L level, voltages on current source wires LE 1 and L 1 are in a precharged state at ground voltage GND at all times by an action of voltage setting circuit 157 .
  • FIG. 48 is an operating waveform diagram describing operations in a case where a non-volatile memory device 1700 according to the sixth modification of the sixth embodiment enters a write state in error when power is turned on. Note that in this case, external write signal Ext.WE and external address Ext.Add that selects no write digit line WDL are simultaneously inputted in error to non-volatile memory device 1700 from outside.
  • LE 1 and L 1 show a change in current flowing current source wires LE 1 and L 1 .
  • WDL shows a change in write current flowing in write digit line WDL.
  • non-volatile memory device 1700 in a case where the memory device enters a write state in error when power is turned on using FIGS. 39 , 46 , 47 and 48 .
  • External voltage Ext.Vcc 1 starts to rise at time point t 1 after power is turned on.
  • external address Ext.Add is inputted to internal address generating circuit 150 and converted to internal row address signal IAdd.
  • external write signal Ext.WE is also inputted to inverter 142 .
  • NAND circuit 301 driven by power supply voltage Vcc 2 in address decode circuit 350 also starts to become active.
  • internal row address signal IAdd not selecting write digit line WDL has been inputted to NAND circuit 301 . That is, when NAND circuit 301 is activated, output signal /SL thereof is set to H level. In a state where no sufficient voltage is supplied to NAND circuit 301 , signal SL outputted from inverter 302 takes H level before /SL takes H level.
  • N-channel MOS transistor 149 c in voltage detecting circuit 159 is turned on, and signal WE at L level rises to H level at time point t 5 at which external clock Ext.CLK starts to fall from H level to L level.
  • a period in which signal WE maintains H level thereof is determined by the number of inverters and characteristics thereof in one-shot pulse generating circuit 320 .
  • signal WE takes H level immediately after external power supply voltage Ext.Vcc 2 reaches a predetermined level when power is turned on.
  • signal WE transits from L level to H level when external clock Ext.CLK transitions from H level to L level. Therefore, even during a resultant longer period from immediately after power is turned on till signal WE takes H level, no chance arises that erroneous data writing is performed on a memory cell.
  • non-volatile memory device 1600 not only does external clock Ext.CLK or external write signal Ext.WE take L level, but signal WE also takes L level.
  • the signal WE takes L level when a predetermined time elapses thereafter by an action of one-shot pulse generating circuit 320 .
  • non-volatile memory device 1700 In non-volatile memory device 1700 according to the six modification of the sixth embodiment, as described above, an effect similar to the effect of the fourth modification of the sixth embodiment.
  • a non-volatile memory device 1700 a is different from non-volatile memory device 1600 a according to the fifth modification of the sixth embodiment shown in FIG. 42 by comparison in an aspect that a control circuit 220 a is provided instead of control circuit 178 . Since the other constituents in the configuration are similar to corresponding constituents in the configuration of non-volatile memory device 1600 a , none of detailed descriptions thereof will be repeated.
  • Control circuit 220 a is different from control circuit 178 by comparison in an aspect that a one-shot pulse generation control circuit 310 is included instead of NOR circuit 163 .
  • non-volatile memory device 1700 a enters a write state in error when power is turned on are similar to those in non-volatile memory device 1600 a of the fifth modification of the sixth embodiment with the exception that a one-shot pulse of signal WE occurs when first external clock Ext.CLK transitions from H level to L level; therefore no detailed description thereof will be repeated.
  • signal WE takes H level immediately after external power supply voltage Ext.Vcc 2 reaches a predetermined level when power is turned on.
  • signal WE transits from L level to H level when external clock Ext.CLK transits from H level to L level. Therefore, even during a resultant longer period from immediately after power is turned on till signal WE takes H level, no chance arises that erroneous data writing is performed on a memory cell.
  • non-volatile memory device 1600 a not only does external clock Ext.CLK or external write signal Ext.WE take L level, but signal WE also takes L level.
  • signal WE takes L level when a predetermined time elapses thereafter by an action of one-shot pulse generating circuit 320 .
  • non-volatile memory device 1700 a In non-volatile memory device 1700 a according the seventh modification of the sixth embodiment, therefore, an effect similar to the effect of the fifth modification of the sixth embodiment.
  • a non-volatile memory device 2000 is different from non-volatile memory device 1000 according to the first embodiment by comparison in an aspect that further provided are power supply terminals 10 # 2 and 20 # 2 , and current sources I 1 # 2 and I 2 # 2 .
  • Non-volatile memory device 2000 is further different from non-volatile memory device 1000 by comparison in aspects that memory array mats 100 d and 200 d are provided instead of memory array mats 100 and 200 , respectively, that a power terminal 10 # 1 and a current source I 1 # 1 are provided instead of power supply terminal 10 and current source I 1 , respectively, and that a power terminal 20 # 1 and a current source I 2 # 1 are provided instead of power supply terminal 20 and current source I 2 , respectively.
  • Memory array mats 100 d and 200 d are each divided into four memory blocks MAB## as an example. Though details are described later, each of the memory blocks MAM# includes as an example, a plurality of memory cells arranged in rows and columns, an address decoder, bit lines, write digit lines and read word lines. Note that a memory array mat may also be of a configuration in which one address decoder selects a bit line, a write digit line and a read word line included in a plurality of memory array blocks.
  • Non-volatile memory device 2000 is further different from non-volatile memory device 1000 by comparison in aspects that current control signals ICNT 1 and ICNT 2 are inputted to respective current sources I 1 # 2 and I 2 # 2 from control circuit 800 , and that currents from current sources I 1 # 2 and I 2 # 2 are supplied to each memory block MAB## in memory array mat 100 d and to each memory array block MAB## in memory array mat 200 d through respective current source wires LE 1 a and LE 2 a . Since the other constituents in the configuration are similar to corresponding constituents in the configuration of non-volatile memory device 1000 , none of detailed descriptions thereof will be repeated.
  • Power supply terminals 10 # 1 , 10 # 2 , 20 # 1 and 20 # 2 supply power supply voltage Vcc to respective current sources I 1 # 1 , I 1 # 2 , I 2 # 1 and I 2 # 2 .
  • Current sources I 1 # 1 and I 2 # 1 supply currents to each memory array block MAB## in memory array mat 100 d and to each memory array block MAB## in memory array mat 200 d , respectively, through current source wires LE 1 and LE 2 .
  • FIG. 51 is a circuit diagram showing a configuration of a memory array 700 in memory array block MAB## according to the seventh embodiment. Note that in FIG. 51 , for convenience in description, current sources I 1 # 1 and I 1 # 2 not included in memory array 700 are also shown in the figure.
  • Memory array 700 is of a configuration similar to that of memory array 500 by comparison and part of the configuration thereof is not depicted in the figure, which part is not necessary for causing currents to flow in bit lines BL and /BL and includes current source I 1 , current source wires L 1 and L 1 #, row decode transistor RD, dummy row decode transistor RDd, row decoder 50 and data write circuit 40 . Instead, current sources I 1 # 1 and I 1 # 2 are depicted.
  • Current source I 1 # 1 supplies currents to a bit line driver 46 causing a write current to flow into bit line /BL and to a bit line driver 30 a causing a write current to flow into bit line BL.
  • Current source I 1 # 2 supplies currents to a bit line driver 45 a causing a write current to flow into bit line /BL and to a bit line driver 30 causing a write current to flow into bit line BL. Since the other constituents in the configuration and operations therein are similar to corresponding constituents of the configuration and operations therein of memory array 500 , none of detailed descriptions thereof will be repeated. While in memory array 700 , a configuration is shown in which bit line drivers are provided to respective bit lines /BL and BL, arrangement of bit line drivers are not limited specifically to these locations. For example, bit line drivers may also be arranged at locations in the vicinity of the centers of bit lines /BL and BL.
  • current sources I 1 # 1 and I 1 # 2 are activated according to current control signal ICNT 1 .
  • Current sources I 2 # 1 and I 2 # 2 are activated according to current control signal ICNT 2 .
  • control signal CT is set so that control circuit 800 transmits current control signal ICNT 1 to current sources I 1 # 1 and I 1 # 2 .
  • control signal CT is set so that control circuit 800 transmits current control signal ICNT 2 to current sources I 2 # 1 and I 2 # 2 .
  • one memory array mat is divided into two parts and current sources are provided correspondingly to respective parts thereof and the parts thereof are selectively activated; thereby enabling a wiring length from a current source to a selected memory cell to be halved.
  • wiring resistance from the current source to the selected memory cell is also halved, thereby enabling fluctuations in write currents can be reduced.
  • non-volatile memory device 2000 according to the seventh embodiment as described above, there can be obtained an effect similar to the effect of non-volatile memory device 1000 according to the first embodiment in connection with a bit line.
  • a non-volatile memory device 2100 is different from non-volatile memory device 2000 according to the seventh embodiment by comparison in an aspect that a configuration is adopted in which in memory array mat 100 d , a wiring length LE 1 from current sources I 1 # 1 to each memory array block MAB## and a wiring length LE la from current source I 1 # 2 to each memory array block MAB# are equal to each other, and in memory array mat 200 d , a wiring length LE 2 from current source I 2 # 1 to each memory array block MAB## and a wiring length LE 2 a from current source I 2 # 2 to each memory array block MAB## are equal to each other. Since the other constituents in the configuration and operations therein are similar to corresponding constituents in the configuration and operations therein of non-volatile memory device 2000 , none of detailed descriptions thereof will be repeated.
  • non-volatile memory device 2100 according to the first modification of the seventh embodiment can also obtain an effect similar to the effect of non-volatile memory device 1100 according to the first modification of the first embodiment in connection with a bit line as well.
  • a non-volatile memory device 2200 is different from non-volatile memory device 2000 according to the seventh embodiment by comparison in an aspect that further provided are power terminals 10 # 3 , 10 # 4 , 20 # 3 and 20 # 4 , and current sources I 1 # 3 , I 1 # 4 , I 2 # 3 and I 2 # 4 .
  • Power terminals 10 # 3 , 10 # 4 , 20 # 3 and 20 # 4 supply power supply voltage Vcc to current sources I 1 # 3 , I 1 # 4 , I 2 # 3 and I 2 # 4 .
  • Current sources I 1 # 3 and I 1 # 4 supply currents to memory array blocks MAB## in memory array mat 100 d through current source wires LE 1 and LE 1 a .
  • Current sources I 2 # 3 and I 2 # 4 supply currents to memory array blocks MAB## in memory array mat 200 d through current source wires LE 2 and LE 2 a . Since the other constituents in the configuration thereof are similar to corresponding constituents in the configuration of non-volatile memory device 2000 , none of detailed descriptions thereof will be repeated.
  • Control circuit 800 transmits current control signal ICNT 1 to current sources I 1 # 1 , I 1 # 2 , I 1 # 3 and I 1 # 4 according to control signal CT.
  • Control circuit 800 transmits current control signal ICNT 2 to current sources I 2 # 1 , I 2 # 2 , I 2 # 3 and I 2 # 4 according to control signal CT.
  • Current sources I 1 # 1 , I 1 # 2 , I 1 # 3 and I 1 # 4 are activated according to current control signal ICNT 1 .
  • Current sources I 2 # 1 , I 2 # 2 , I 2 # 3 and I 2 # 4 are activated according to current control signal ICNT 2 .
  • control signal CT is set so that control circuit 800 transmits current control signal ICNT 1 to current sources I 1 # 1 , I 1 # 2 , I 1 # 3 and I 1 # 4 .
  • control signal CT is set so that control circuit 800 transmits current control signal ICNT 2 to current sources I 2 # 1 , I 2 # 2 , I 2 # 3 and I 2 # 4 .
  • Non-volatile memory device 2200 according to the second modification of the seventh embodiment can therefore obtain an effect similar to the effect of non-volatile memory device 1200 according to the second modification of the first embodiment in connection with a bit line as well.
  • the configuration is shown in which for one memory array mat, two current sources are connected to corresponding respective two current source wires, three or more current sources are connected to current source wires, thereby enabling a write current flowing to a memory block of a memory array mat to be further stabilized.
  • an example is shown in which a plurality of current sources connected to respective two current source wires corresponding to one memory array mat are all activated, the present invention is not limited to such a configuration.
  • the present invention can also be applied to a configuration in which a signal from a control circuit is transmitted to each of current sources independently of the other to enable a desired current source to be selectively activated by the control circuit.
  • FIG. 54 is a conceptual diagram showing a configuration of a memory array 705 in a memory array block MAB## according to an eighth embodiment.
  • FIG. 54 there is typically shown only part of the configuration for causing a current to flow into bit line.
  • FIG. 54 for convenience in description, there are also shown current sources I 1 # 1 and I 1 # 2 not included in memory array 705 .
  • memory array 705 includes read/write control circuits 210 and 211 .
  • Bit lines BL 1 to BLn to which a plurality of memory cells (not shown) are connected are provided in a row direction between read/write control circuits 210 and 211 .
  • Read/write control circuits 210 and 211 are connected to ground voltage GND through respective current source wires L 1 a # and L 0 #.
  • Current sources I 1 # 1 and I 1 # 2 are connected, through respective current source wires L 0 and L 1 a , to locations on read/write control circuits 210 and 211 in the vicinity of locations thereon to which bit line BL 1 is connected.
  • Current source wires L 1 a # and L 0 # are connected to locations on read/write control circuit 210 and 211 in the vicinity of locations thereon to which bit line BLn is connected.
  • Read/write control circuits 210 and 211 when data is read, are simultaneously controlled and read/write control circuit 211 outputs data DOUT read from a memory cell (not shown) connected to bit line BL.
  • Data DIN to be written to a memory cell when data is written, is inputted to read/write control circuit 211 , and read/write control circuits 210 and 211 are simultaneously controlled to write data DIN to a memory cell connected to a desired bit line.
  • read/write control circuits 210 and 211 operate so that current source I 1 # 1 and current source wire L 0 #, to which ground voltage GND is connected, are connected electrically to each other.
  • read/write control circuits 210 and 211 operate so that current source I 1 # 2 and current source wire L 1 a #, to which ground voltage GND is connected, are connected electrically to each other.
  • current source I 1 # 1 connected to current source wire L 0 is located at a position thereon diagonal with respect to ground voltage GND connected to current source wire L 0 #.
  • current source I 1 # 2 connected to current source wire L 1 a is located at a location thereon diagonal with respect to ground voltage GND connected to current source wire L 1 a #.
  • memory array 705 according to the eighth embodiment therefore, there can be obtained an effect similar to the effect of memory array 505 according to the second embodiment in connection with a bit line as well.
  • FIG. 55 is a conceptual diagram showing a configuration of a memory array 710 in memory array block MAB## according to a first modification of the eighth embodiment.
  • FIG. 55 there is typically shown only part of the configuration thereof, which part serves for a current to be caused to flow into bit line.
  • FIG. 55 for convenience in description, there are also shown current sources I 1 # 1 and I 1 # 2 not included in memory array 710 .
  • memory array 710 is different from memory array 705 according to the eighth embodiment by comparison in aspects that current sources I 1 # 1 and I 1 # 2 are connected, through respective current source wires L 0 and L 1 a , to locations on respective read/write control circuits 210 and 211 in the vicinity of the centers between locations thereon to which bit lines BL 1 and BLn are connected, that current source wires L 1 a # 1 and L 1 a # 2 to which ground voltage GND is connected are connected to locations on read/write control circuit 210 in the vicinity of locations thereon to which respective bit lines BL 1 and BLn are connected, and that current source wires L 1 # 1 and L 1 # 2 to which ground voltage GND is connected are connected to locations on read/write control circuit 211 in the vicinity of locations thereon to which respective bit lines BL 1 and BLn are connected. Since the other constituents in the configuration thereof are similar to corresponding constituents in the configuration of memory array 705 , none of detailed descriptions thereof will be repeated.
  • read/write control circuits 210 and 211 operate so that current source I 1 # 1 is connected electrically to current source wires L 1 # 1 and L 1 # 2 , to which ground voltage GND is connected.
  • read/write control circuits 210 and 211 operate so that current source I 1 # 2 is connected electrically to current source wires L 1 a # 1 and L 1 a # 2 , to which ground voltage GND is connected.
  • a memory array 720 is different from memory array 705 according to the eighth embodiment shown in FIG. 54 by comparison in an aspect that further provided are current sources I 1 # 11 and I 1 # 22 and current source wires L 1 a # 1 and L 1 # 1 .
  • Memory array 720 is further different from memory array 705 by comparison in an aspect that current source wires L 1 a # 2 and L 1 # 2 are included instead of current source wires L 1 a # and L 0 #. Since the other constituents in the configuration thereof are similar to corresponding constituents in the configuration of memory array 705 , none of detailed descriptions thereof will be repeated.
  • Current source I 1 # 11 is connected electrically to a location on read/write control circuit 210 in the vicinity of a location thereon to which bit line BLn is connected through current source wire L 11 .
  • Current source I 1 # 22 is connected electrically to a location on read/write control circuit 211 in the vicinity of a location thereon to which bit line BLn is connected through current source wire L 11 a .
  • Current source wires L 1 a # 1 and L 1 a # 2 connected to ground voltage GND are connected electrically to locations on read/write control circuit 210 in the vicinity of locations thereon to which respective bit lines BL 1 and BLn are connected.
  • Current source wires L 1 # 1 and L 1 # 2 connected to ground voltage GND are connected electrically to locations on read/write control circuit 211 in the vicinity of locations thereon to which respective bit lines BL 1 and BLn are connected.
  • read/write control circuits 210 and 211 operate so that current sources I 1 # 1 and I 1 # 11 are connected electrically to current source wires L 1 # 1 and L 1 # 2 , to which ground voltage GND is connected.
  • read/write control circuits 210 and 211 operate so that current sources I 1 # 2 and I 1 # 22 , are connected electrically to current source wires L 1 a # 1 and L 1 a # 2 , to which ground voltage GND is connected.
  • memory array 720 according to the second modification of the eighth embodiment therefore, there can be obtained an effect similar to the effect of memory array 520 according to the second modification of the second embodiment in connection with a bit line as well.
  • a memory array 730 is different from memory array 720 according to the second modification of the eighth embodiment shown in FIG. 56 by comparison in an aspect that none of the following current source wires are included current source wires L 1 a # 1 and L 1 a # 2 to which ground voltage GND is connected and current source wires L 1 # 1 and L 1 # 2 to which ground voltage GND is connected.
  • Memory array 730 is further different from memory array 720 by comparison in an aspect that included are current source wires L 1 a # and L 0 # to which ground voltage GND is connected. Since the other constituents in the configuration thereof are similar to corresponding constituents in the configuration of memory array 720 , none of detailed descriptions thereof will be repeated.
  • Current source wires L 1 a # and L 0 # connected to ground voltage GND are connected electrically to locations on respective read/write control circuits 210 and 211 in the vicinity of the center between locations thereon to which respective bit lines BL 1 and BLn are connected.
  • read/write control circuits 210 and 211 operate so that current sources I 1 # 1 and I 1 # 11 are connected electrically to current source wires L 0 #, to which ground voltage GND is connected.
  • read/write control circuits 210 and 211 operate so that current sources I 1 # 2 and I 1 # 22 are connected electrically to current source wire L 1 a #, to which ground voltage GND is connected.
  • memory array 730 according to the third modification of the eighth embodiment therefore, there can be obtained an effect similar to the effect of memory array 530 according to the third modification of the second embodiment in connection with a bit line as well.
  • a memory array 740 is different from memory array 720 according to the second modification of the eighth embodiment shown in FIG. 56 by comparison in an aspect that further included are power supply sources I 1 # 111 and I 1 # 222 .
  • Memory array 740 is further different from memory array 720 by comparison in aspects that current source I 1 # 11 is connected electrically to a location on read/write control circuit 210 in the vicinity of the center between locations thereon to which bit line BL 1 and BLn are connected through current source wire L 11 instead of a location on read/write control circuit 210 in the vicinity of a location thereon to which bit line BLn is connected, and that current source I 1 # 22 is connected electrically to a location on read/write control circuit 211 in the vicinity of the center between locations thereon to which bit line BL 1 and BLn are connected through current source wire L 11 a instead of a location on read/write control circuit 211 in the vicinity of a location thereon to which bit line BLn is connected.
  • Memory array 740 is further different from memory array 720 by comparison in aspects that current source wire L 1 a # 1 connected to ground voltage GND is connected electrically to a location on read/write control circuit 210 in the vicinity of the center between locations thereon to which current sources I 1 # 1 and I 1 # 11 are connected instead of a location on read/write control circuit 210 in the vicinity of a location to which bit line BL 1 is connected, and that current source wire L 1 # 1 connected to ground voltage GND is connected electrically to a location on read/write control circuit 211 in the vicinity of the center between locations thereon to which current sources I 1 # 2 and I 1 # 22 are connected instead of a location on read/write control circuit 211 in the vicinity of a location to which bit line BL 1 is connected.
  • Current source I 1 # 111 is connected electrically to a location on read/write control circuit 210 in the vicinity of a location thereon to which bit line BLn is connected through current source wire L 111 .
  • Current source I 1 # 222 is connected electrically to a location on read/write control circuit 211 in the vicinity of a location thereon to which bit line BLn is connected through current source wire L 111 a.
  • Memory array 740 is further different from memory array 720 by comparison in aspects that current source wire L 1 a # 2 connected to ground voltage GND is connected electrically to a location on read/write control circuit 210 in the vicinity of the center between locations thereon to which current sources I 1 # 11 and I 1 # 111 are connected instead of a location on read/write control circuit 210 in the vicinity of a location to which bit line BLn is connected, and that current source wire L 1 # 2 connected to ground voltage GND is connected electrically to a location on read/write control circuit 211 in the vicinity of the center between locations thereon to which current sources I 1 # 22 and I 1 # 222 are connected instead of a location on read/write control circuit 211 in the vicinity of a location to which bit line BLn is connected. Since the other constituents in the configuration thereof are similar to corresponding constituents in the configuration of memory array 720 , none of detailed descriptions thereof will be repeated.
  • read/write control circuits 210 and 211 operate so that current sources I 1 # 1 , I 1 # 11 and I 1 # 111 are connected electrically to current source wires L 1 # 1 and L 1 # 2 , to which ground voltage GND is connected.
  • read/write control circuits 210 and 211 operate so that current sources I 1 # 2 , I 1 # 22 and I 1 # 222 are connected electrically to current source wires L 1 a # 1 and L 1 a # 2 , to which ground voltage GND is connected.
  • memory array 740 greater reduction occurs in fluctuations in path lengths from a current source to ground voltage GND, when data is written, caused by locations of selected bit lines than in the configuration of memory array 720 .
  • memory array 740 according to the fourth modification of the eighth embodiment therefore, there can be obtained an effect similar to the effect of memory array 540 according to the fourth modification of the second embodiment in connection with a bit line as well.
  • application of the present invention is not limited to an MRAM device including MTJ memory cells, That is, the present invention can be applied commonly to non-volatile memory devices each provided with memory cells each having a characteristic to change a pass current therethrough when data is read according to a level of binary storage data.

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US6947320B2 (en) 2005-09-20
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US7154777B2 (en) 2006-12-26
JP2004178709A (ja) 2004-06-24
US20070127288A1 (en) 2007-06-07
US20050276111A1 (en) 2005-12-15
US20040100819A1 (en) 2004-05-27

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